FY (or "Fight Yard") is a popular custom map type in Counter-Strike, with no objectives and short rounds. Highrise has a unique FY layout and became fairly popular.
In Highrise, the two teams fight over 3 glass hallways suspended over the street, across two floors. There are two elevators on either side behind where players spawn. The position of the hallways forces players to look in all directions to stay safe. It also encourages ambushing from above. The simple layout hides lots of alcoves to snipe from and paths to take from one side to the other.
The map combines this with the simple joy of watching ragdolls fall long distances.
The original Highrise was very rough. Near the end of 2008 I released a new version (fy_highrise_09) with imroved the graphics.