Surface added! It is very simple in terms of both layout and AI pathfinding. Good for building stuff. Suggestions welcome. Added gas to the jail, for the most misbehaving. Several lighting improvements in areas that were yet uncovered by them. Download size doubled, as a result of adding surface. May improve it in the future.

A couple more lighting improvements, disabled collision on all candle cans, did something else I forgot.

Major lighting improvements, possible fix for ambient sounds not playing in multiplayer, fixed visual inconsistencies unrelated to lighting. Removed the lone spawn.

Minor changes in optimization, slight adjustments to map and AI nodes, made debris models work, removed small door at the bridge pit and added toxic waste at the bottom to keep it more consistent with the theme. Teleports now teleport things in batches instead of one at a time, for a more consistent group experience and less broken physics with entities constrained to other entities. Don't try driving a car in the longest tunnel, I made an attempt to stop it, as it causes serious physics buggery.

Improved framerates at bridge noticably. Fixed broken lighting on a brush in northmost metro tunnel. Further optimization at various places. Download size cut by half(!)

Further optimization, fixed broken areaportal in a door, removed props that showed up as errors.

Fixed more broken areaportals.

Fixed a broken areaportal. Again. Improved AI navigation in stairs. If the AI does not work, delete rp_metro_refuge.ain from garrysmod/maps/graphs and run ai_norebuildgraph 1 in the console before opening the map.

Fixed a broken areaportal.

Removed water around bridge area to improve framerates, did a thing at far end of the bridge, fixed overlays on certain detail brushes, more optimization.