Half-Life: Source/Environmental Map Textures
This is a sub-page of Half-Life: Source.
Half-Life: Source has several unused environmental map textures, all of which come from maps that never got released ports to the Source engine.
Deathmatch Classic environmental maps
The game has environmental maps of several levels from Deathmatch Classic, despite that game never being ported to the Source engine.
The lighting suggests these were taken in the Source engine, not from the original game's engine.
Two environmental maps for the DMC level dm2 exists.
DMC's dm3 has two as well.
And DMC's E1M2 has a whopping four environmental maps for it!
Not to be outdone, p_se_3 has four environmental maps too!
Team Fortress Classic environmental maps
An environmental map for a Team Fortress Classic level is also in the game's files, despite TFC never having a released port to the Source engine too.
These appear to be textures taken from the water near the blue base in the TFC level cz2.
Unlike the DMC environmental maps, this one does not have the water in the level rendered properly.