D&D Notable Location - Underdark

A location that is known locally or further afield, as a landmark, place of history, magical danger or otherwise noteworthy.
The Underdark is a place of twisting tunnels, constant darkness and strange magic. Encounters might occur in a forest of fungi, amid giant stalactites or by the side of a gaping chasm. It is a place of elemental earth and gates to far realms. Home to fungi creatures, the dark elves and aberrations from the Far Realms.

tools for - dnd5e location quest underdark

terrain:

At the bottom of a wide pit rocks creak and shift. Occasionally geysers scatter stones and metal chunks through the area.
The Long Vale is a mushroom ring. It is at a crossroads. It is desecrated ground. is said that the Solemn Aerie of Runecross is nearby..
A sunken ruins. is part of an ongoing struggle between powerful monsters.
A noisy waterfall descends into a lake of clear water. On an island covered in glowing green mushrooms is a portal to the surface.
A beautiful crystal statue. It is at a crossroads. It is disguised by a hallucinatory terrain. has been ripped from another realm.
The Planar Forge of Wraith's Falls is a ghostly fungal forest. It is often home to insects. It is associated with rothe.
A magnificent Rift. It has a crossing to another plane. It is associated with a powerful shadow spirit. has the burial site of the diamond dragon.
Builder's Halls is a gloomy hot springs. It is in a field. It is touched by druidic magic.
A dwarven gorge. It is cursed by a god.
An overgrown clearing. It is in a field. It is associated with a fallen champion. has the tomb of a wise archmage.