A weird version of the Citadel.
The Citadel went through many different incarnations before the retail release. In early development it was depicted as a vast organic spire that seemed to be growing out of the ground. Eventually this design was reconfigured to be a metallic structure with the same basic shape as the organic version. Somewhere along the way the Citadel became a short, round metallic structure with several auxiliary structures attached to it. Finally all of these versions were scrapped in favor of a more monolith like tower.
As for the actual interior of the Citadel, it seems that somewhere along the way the Combine were really big into ceramic tiles. This cannot be attributed to any misnamed textures, as the tiles exist in many of the early Citadel's composite textures. I don't know what theme Valve was going for, but there it is.
Prototype of old Citadel interior with tiles.