The Grand Necropolis

Elves are hard to kill biologically. Although they have a reputation for being less constitutional than Humans, they have long lives and hearty immune systems. They can live for 750 years, making them functionally immortal compared to humans and other races.
This makes it all the more tragic when an elf fails to reach that age, cut down by violence, misadventure, or one of the few illnesses that affect the fair folk.
In the time of Abhaile, dead elves and Half-Elves (and those few peoples of other races who earned the honour) would lie in state in the Grand Necropolis. Large enough to be a city of its own, the dead bodies were tended to by necromancers, who would preserve them in beautiful tombs. Twice a year, elves would pay visits to their dead in a joyful occasion where necromancers could bring those who were still unsettled back to speak to their families and loved ones.
During the fall of Abhaile, necromancers evacuated the living citizens into the maze of the mausoleums, using the dead as a guard against being attacked. Their Chief of Staff, Lethe, personally redirected attention away from the living and many who sought refuge in the Necropolis were later able to escape and found New Abhaile.
The Grand Necropolis fell to the Shadow Demons around 8BS. Nobody has heard anything from inside it since. If the dead still roam its halls, they do so silently.