Legend has it that a voracious Purple Worm burrowed out these tunnels long ago. After the worm left, a couple generations of sentient creatures found it easier to move in than to dig through stone themselves.
Some notable features:
The chevron arrows point up slopes.
A1 An elevated platform with a ladder up to it on the left side.
A5 & G7 Irregular pits
B4 I don't know what this is yet. Maybe a mysterious energy field, maybe a plug that fills in a vertical shaft that goes down into the route the worm departed from here to deeper parts unknown.
C7 Another vertical hole from an upper tunnel down to the lower tunnel where a groundwater spring feeds a pool.
D5 metal bar walls and gates.
E2 Partial cave in of both the upper and lower tunnels. There is a
hole in the floor of the upper one that opens through the ceiling of the
F2 The cave in blocks the entrance of an old temple with undead occupants.
G5 The entrance to the burrow.
(I drew this over my morning mocha. I will rescan a straighter image later.)