Funland
Funland, an amusement park in the GTA IV rendition of Liberty City located in Firefly Beach in the Firefly Projects, south Broker, and is based on Coney Island in New York City. Though Funland is not an interactive location, it can be visited in-game. Some attractions include "The Screamer", a roller coaster, tea cups and mini-golf.
Sidestory
During the mission First Date, Niko suggests they visit the "fun fair", just a short drive away. When you arrive, your date notes that the location is closed, and probably wouldn't pass safety regulations.
Trivia
In the mini-golf track there are different structures, they all make resemblance to older GTA games.