Whiskey Peak is one of the major cities (and only city fully explored) located on Cactus Island.
This city is inhabited entirely by bounty hunters working for Baroque Works, who capture any bounty heads that land here to help fund Baroque Works' missions. As such, the city does not have much treasure or supplies, as noted by Nami and Miss Monday. The citizens here fool pirates into thinking that they are kind and hospitable and proceed to throw a party for them, only to turn them in and steal everything from their ship when the pirates pass out. Whiskey Peak is apparently famous for its liquor, but whether that is the truth or an excuse to have many barrels of alcoholic beverages to better subdue pirates without suspicion is unknown. Roronoa Zoro defeated 100 bounty hunters here, including Mr. 9, Miss Monday, Igaram, and Vivi. Apparently, in addition to Whiskey Peak there are several other bases like this in the area.
After the timeskip, Mr. 9 and Miss Monday are revealed to be living there and are raising a family.