The Community Center is located in South Bohan. It's a social gathering center where neighbourhood residents can practice sports and participate in various arts programs. The center is run by Manny Escuela and also acts as the "headquarters" for his St. Mary's Community Project, an outreach program meant to help gangbangers and petty criminals leave their lives of crime.
During GTA IV, Niko Bellic frequents the community center to receive missions from Manny, who pays Niko to eliminate criminals and gangsters from the area, both to (as Manny puts it) "clean up the streets" and to help further Manny's career as a reality TV star.
If you manage to enter the Center via cheats, then you can hear The Classics 104.1 blasting inside.