Sewer. More of a loose conglomeration of little areas than a single proper one, they're not even joined up.

Area
Name
zMUD dirs
Walking dirs
Town of Solace The forgotten sewers
nw, 2w, 4n, e, look painting, open n, n, 23w, 6n, e, open d, d
Revelation City The Old, Filthy Sewer
6n, 3nw, w, n, 4e, s, w, sw, s, sw, 2s, 2sw, 2s, 2ne, n, nw, w, 2nw, w, 3nw, 3w, 2nw, 3w, 5nw, w, 3n, e, en, open d, d
Raven Tor The Old Dungeon Sewer System
6n, 3nw, w, n, 4e, s, w, sw, nw, n, ne, u, 2ne, u, ne, u, ne, nw, w, u, 2ne, u, w, u, ne, se, 2e, 2se, e, d, ne, 2e, u, give 100k coins henry. give 300k coins henry. d, 4w, 2n, doorbash n, 3n, w, e, n, u, nw, 4s, doorbash s, s, d, doorbash d, d
Morgul Vale Deep within the Sewer
nw, 2w, 4n, e, look painting, open n, n, 49w, 8s, 2sw, 2s, u, 2s, 2w, 2sw, s, se, sw, 3e, pick/doorbash/knock e, open e, e, s, 2e, d, w, open d, d
Thalos The slime infested sewers
6s, ne, 2s, se, 2e, s, 2sw, s, 4sw, 4s, 5se, 2s, d, s, se, s, 3se, 4e, 6s, sw, 3w, 3n, w, open d, d
Wastelands Cave tunnel
6s, ne, 2s, se, 2e, s, 2sw, s, 4sw, 4s, 2sw, s, 2sw, s, sw, 2s, w, sw, s, 2sw, s, w, 2s, sw, s, sw, se, e, ne, open wall, n
Transylvania The leech infested Sewers
13s, 2e, 2u, e, 3se, d, s, 4se, e, se, e, ne, nw, n, u, 3n, 3w, n, e, open d, d
Darkhaven Darkhaven's offal-slimed sewers
6s, open manhole, d
King's Castle The Dank Sewers
13e, 3s, 3e, 2ne, 3se, e, 2s, sw, s, se, s, se, 2e, 2ne, e
Ocean Keep The Sewer Labyrinth
8e, 3ne, 3e, ne, e, ne, 2e, 5n, ne, e, ne, e, se, e, ne, 3n, ne, 2d, 4w, 4n, e, s, open d, d
Kontaur n/a 26w, 9s, d, 2s, e, n, e, 2s, e, 4s, e, 2s, unlock/open s, 7s, d, s, w, 2n, e, open d, d