The Undergate addon - DarkPlaces Classic Set mod for Quake
Cmdlne: -game undergate +map undergate Selector map that allows you to look around the map, find what you want to play, go thru the teleporter, play the map and assuming you finish it, returns you back to the selector map. Historical archive.
Ruohis Primevi Rygel Darkplaces Darkplaces Classic Set Mod For Quake He Undergate Ingleplayer Maps Ultiplayer Maps
Source: moddb.com