The prison_grav.zip file you have requested: Maps Levels Missions / Deathmatch / O to P Titles / DM: Prison Grav - 142.11kb is not available. Perhaps try browsing all files for the game Half-Life 2 and upload any files you want to share or are missing. This is the only information we could locate:
One challenge will be designing the map so that the cell-block & hallway areas are fun too. Update: I got online with it and had some fun. Unfortunately my machine lags everyone out pretty bad once I get more than 5 people on the server Note: The basic Idea is Cell-block type rooms around the perimiter (players spawn in these).