The Whole Cake Chateau was the four-layered massive castle of Big Mom, located at the center of Whole Cake Island. Following the detonation of the bomb inside the Tamatebako, extensive damage was caused to the Chateau's base, resulting in the collapse of the entire castle. Streusen transformed the building into spongecake in order to dampen the impact, thus causing the resultant product to cover Sweet City.
Whole Cake Chateau was the largest cake building found in Sweet City. The Chateau's exterior resembled a four layered cake, with the three top layers in different sizes, and each layer had a different style (horizontal, vertical, slash with horizontal base, and backslash), although internally it had a total of ten floors. The second layer had thin, red leafed trees on it edges, which gave the cake shape structure the resemblance of a birthday cake with lit candles. Another tree was occasionally seen on the top layer as well. The third layer had the kitchen's chimney on top of it across the fourth one. As the Chateau collapsed, it was transformed into a sponge cake, and the fourth layer was cut vertically.
The Chateau dwarfed essentially all the other buildings and landmarks of the island (actually being larger than Sweet City as a whole). It was situated roughly centrally on the island, being surrounded by Sweet City and Lake Aprico.
The Baum (バウム Baumu?) is the name of the hallways in the Chateau. Luffy ran through one on the third floor, while he looked for Sanji. Another one on the second floor was partly destroyed when the chateau collapsed. Baum is German for "Tree", and considering the overall food theme, might come from Baumkuchen or Baumstriezel, which are types of Spit Cake, a kind of European cake made from rolled dough.
In the anime, there are five floors, with an additional floor with a slash outer design between the first and second floors.
After the collapse of the Chateau, everything from the second floor upward was destroyed.
- The Prisoner Library (囚人図書室 Shūjin Tosho-shitsu?) is where Big Mom keeps her prisoners inside the World of "Books" using her nineteenth son, Charlotte Mont-d'Or's ability. The known prisoners were Monkey D. Luffy and Nami. Numerous books are stored in the Prisoner Library, and the one within which prisoners in the process of being tortured or questioned faces a large sofa where executives can sit while talking with the prisoners.
- The Meeting Room (会議室 Kaigi-shitsu?) was where members of the Big Mom Pirates can meet to discuss current events in Totto Land
- The Guest Rooms (客間 Kyakuma?) were where guests of the island may reside, particularly those awaiting a marriage. There was at least one guest room on the second floor.
- The Einbaum Meeting Room (アンバウム会議室 Anbaumu Kaigi-shitsu?) was located on the eastern side of the second floor. Einbaum is german for "Dugout".
- The Courtyard (中庭 Nakaniwa?) was a large room located on the third floor of the Chateau. It had large windows with bright curtains. It was decorated to appear like an outdoor garden, with a cloudy wallpaper, plants, rose archs, and gazebos. It also had a large table where Big Mom can dine with her guests, with a large seat fitting the Yonko's great size.
- Pudding's Room (プリンの部屋 Purin no Heya?) was where Pudding resides. The door to the room was a talking door that wouldn't open to unexpected people when its master was busy. The room also had access to a wide balcony overlooking the island.
- An Infirmary (医療室 Iryō-shitsu?) was situated on the Chateau's third floor. It was there that Vinsmoke Reiju was taken for treatment and rest after being attacked by Pudding.
- There was an unspecified Einbaum (アンバウム Anbaumu?) which was located on the third floor. It had large windows, covered by thick curtains.
- The Room of Treasure (宝物の間 Hōmotsu no Ma?) was a large room located on the fourth floor of the Chateau. It was where Big Mom stores her most valuable treasures, including three poneglyphs, one of which was her Road Poneglyph. The unique door leading to that room was very tough, although Big Mom easily destroyed it. It is noted that even her children are not so easily granted entry to this room.
- The Alcohol Storehouse (酒貯蔵庫 Sake Chozōko?) was located next to the Room of Treasure. It was filled with barrels.
- A Women's Bathroom (女子トイレ Joshi toire?) was also located on the fourth floor, and possess mirrors that connect to the Mirro-World.
- There was at least one other Infirmary on the fourth floor.
- There were at least two Guest Rooms in the sixth floor. One was inhabited by Vinsmoke Sanji, while the other was inhabited by the rest of the Vinsmoke Family.
- The Giant Kitchen (巨大キッチン Kyodai Kitchin?) was where the preparations for big events are held, and where the cake for Pudding's and Sanji's wedding was made. It was ran by Streusen.
- Big Mom's Bedroom (ビッグマム寝室 Biggumamu Shinshitsu?) was where Charlotte Linlin, Napoleon, Prometheus, and Zeus spend their nights. The room had a large mirror that connects to the Mirro-World.
- The Bride and Groom's Room (新郎新婦控え室 Shinrō Shinpu Hikaeshitsu?) was where the betrothed couple waited before their wedding ceremony. It was a large hall with a picture of the Whole Cake Chateau and other baked goods.
- The Party Hall (お茶会会場 Osakai kaijō?, lit: Tea Party Venue) was a large outdoors space where big events such as the tea parties were held. It had a large double-door homie at the entrance and a large staircase from which Big Mom entered to greet her guests. Like most of Totto Land, everything in the room was edible, and there were several homies who serve drinks and snacks. Several tables were disposed in a staggered arrangement, where guests can sit and chat. Charlotte Smoothie was also making drinks for the guests thanks to her ability.
- The Queen's Chamber (女王の間 Joō no Ma?) was a two story room, where Big Mom usually resided. It had a throne adapted for Linlin's great size, which was adorned with sweets and candies. Several supersized ice cream cones and bowls, alongside other sweet food, are standing and laying around her throne. The Queen's Chamber was also where she could discuss with people about matters such as alliances, departures, demands, or requests. After the Chateau collapsed, Big Mom was shown sitting upright in her chamber, indicating the room was below where the building broke, or on the higher level Streusen cut off. The anime depicts this room to be on the eighth floor.
- The Library (図書室 Tosho-shitsu?) was where Big Mom collects, categorizes, and stores in large books the special creatures she finds interesting, where they do not age thanks to Mont-d'Or's ability. Some of the captured creatures are: a manticore from Impel Down, a unicorn, a Doskoi Panda, a kinokobito, a centaur from Punk Hazard, a griffin from South Blue, a longlimb, and a dinosaur. According to the anime, it is located in the fifth floor.
- Galette's Room (ガレットの部屋 Garetto no Heya?) is where Charlotte Galette resides. In the room, there is a closet with a mirror connected to the Mirro-World.
- The Execution Room (処刑場 Shokei-jō?) is a room with bones and a mirror connected to the Mirro-World.
During the TimeskipEdit
During one of Big Mom's tea parties, someone unintentionally made Mother Carmel's picture fall from its chair. In response, Big Mom started to emit a shrieking cry that stunned the assembly and unleashed Haoshoku Haki waves, making the guests collapsed one after another. Out of psychological shock, she fell on her knees, scraping them and injuring herself for the first time in a long time.
Fishman Island ArcEdit
While preparing for a tea party, Big Mom was informed by Bobbin that Fishman Island had failed to provide its requisite amount of sweets for her. She then tried to contact Pekoms and Tamago, but she conversed with Monkey D. Luffy, who took responsibility for eating the sweets, convincing her to transfer her grudge to him instead.
Whole Cake Island ArcEdit
After one of Big Mom's food cravings three days before the wedding between Charlotte Pudding and Vinsmoke Sanji, Big Mom and Jinbe talked about him leaving her crew, which she agreed to as long as he spun a roulette wheel to lose something in return. Knowing that all the options would lead to his death, Jinbe backed out of the deal.
The next day, Big Mom forced Caesar to continue working on his gigantification research in a new lab constructed by Charlotte Perospero, giving him two weeks to complete it. Later, she sent Sweet Commander Charlotte Cracker to ensure the Sanji Retrieval Team would be taken out. After an 11-hour battle, Luffy managed to defeat Cracker, sending him flying into Sweet City and crashing into the Chateau. Cracker's defeat caused Sweet City to be put into a state of lock down, and an army was sent to take out the Straw Hats, marching from the Chateau to the outskirts of Sweet City, where after a long fight, the army defeated Luffy and Nami and captured them.
Luffy and Nami were imprisoned inside a book in the Prisoner Library, while the Vinsmoke Family met with Big Mom and Pudding. Sanji agreed to marry Pudding as long as Big Mom freed Luffy and Nami. Big Mom agreed to this, but never intended to honor it. Meanwhile, Brook and Pedro infiltrated the Chateau as they sought to steal Big Mom's Poneglyphs. Pedro fought Big Mom's guards in the Chateau as a distraction before confronting Tamago in the courtyard, while Brook slipped into the Room of Treasure and transcribed the Poneglyphs. Big Mom discovered Brook's presence and attacked him, eventually defeating him, but Brook had managed to get copies of the Poneglyphs. Meanwhile, Pedro ended his battle with Hiyoko by setting off a large number of bombs in his jacket to cover his escape into the Mirro-World with the help of Carrot and Chopper.
Meanwhile, Jinbe broke into the Whole Cake Chateau and attacked Opera at the Prisoner Library, freeing Luffy and Nami. Luffy went on ahead to warn Sanji, while Nami and Jinbe fought hordes of Big Mom Pirates until Chopper and Carrot brought them into the Mirro-World. Big Mom used Brook as a plaything and slept with him, and after a grueling effort, the team managed to retrieve Brook. Meanwhile, Sanji discovered that the Big Mom Pirates intended to massacre his family at the wedding, and after much convincing and self-reflection, he decided to go back to Luffy. Elsewhere at the Chateau, Luffy encountered Vinsmoke Reiju on the fourth floor infirmary and learned Sanji was aware of Big Mom's plot and decided to meet him at the place where he promised he would wait for the cook.
At the day of the wedding, the tea party and wedding ceremony then started on the top of the Chateau, and before the Big Mom Pirates could assassinate the Vinsmokes, Luffy burst out of the wedding cake and invaded the venue as part of the Straw Hats and the Fire Tank Pirates alliance's plan. During the chaos that followed, Brook shattered Big Mom's portrait of Mother Carmel, causing her to have a crisis and weakening her. However, Big Mom foiled the Fire Tanks' assassination attempt by screaming, and the Big Mom Pirates lay siege to the Straw Hat-Fire Tank alliance. Even after the Vinsmoke Family joined their side and they tried a quick escape, the alliance was routed by Big Mom and her crew. However, the Tamatebako suddenly fell off the Chateau as some of her wedding guests scuffled over it, causing a massive explosion at its base that caused the entire structure to topple over. Streusen turned the venue into soft cake, saving everyone from the fall, and the Big Mom Pirates prepared to go after the enemy alliance, who had flown away to the northwest part of the island.
At the foot of the collapsed Chateau, the Big Mom Pirates strategized their next move, but Big Mom started craving for wedding cake, causing her eating disorder to act up. She went on a rampage through Sweet City, and Perospero lied that the Straw Hats had a backup cake, causing Big Mom to go and pursue them through the Seducing Woods. The Big Mom Pirates split their forces to go after the alliance factions, and several of them joined Big Mom in her chase of the Straw Hats.
While the majority of the Big Mom Pirates pursued the Straw Hat-Fire Tank alliance members, some stayed to coordinate their forces under Mont-d'Or's orders. When they learned that the territorial sea slugs went missing, Mont-d'Or was shocked, and he later added the Sun Pirates to their list of enemies. As reports of Luffy and Katakuri's fight in the Mirro-World came in, Stussy revealed to Mont-d'Or that the collapse of the Chateau was caused by the Tamatebako they obtained from the Straw Hats. As the time for the Straw Hats' planned rendezvous on Cacao Island drew closer, Mont-d'Or promised Morgans that the Big Mom Pirates would crush the Straw Hats.
After the Straw Hats escaped and Big Mom regained her sanity, she returned to her destroyed castle and received news about the chaos at Totto Land was reported to the world. Big Mom read the news and swore revenge against Luffy and Morgans. A few days later, Big Mom called Kaido from her chamber and used his debt to her to demand that she would be the one to kill Luffy despite both of them having a grudge against him, and offered him to work together.