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:

A floating ravine. It is in a field. It is a place where mammals often congregate. It is associated with a magical fiend.
Ruins of Cockle's Down is an exposed ruins. It is often home to swans. was where a demigod was born.
A bronze chain marks a ford through a sparkling river. Anything entering the river sparkles with dim light for 1d4 hours afterwards.
Slayerthorpe Grove is a pretty burial chamber. It is at the edge of a lake. It is associated with fiends. It is associated with a dangerous myconid. was a place of executions.
A colorful valley. It is a place where mammals often congregate. was the site of a renowned battle - dwarves destroyed dwarves and a ruler's tomb is build here.
A cursed stalagmite house. It is in a meadow. It is associated with a power of peace.
Bats infest this cave, their droppings covering an ancient obsidian arch. Water runs down it from an overflowing pool on a ledge above.
The Hold of Fire is a cursed Isle. It has a festival that occurs monthly.
A reflective ruins. It is at a crossroads. It is associated with undead. It is protected by a ghost. was where a fey portal was built.
Dread Falls. A waterfall plunges into treacherous rapids. Several altars of metal and crystal float in the waters. Fiends watch this place.