Lore
A great undead city that once held a thriving culture. When the Four Kings that ruled it fell to the Abyss and their knights were corrupted, and it became a cesspool of ravenous Darkwraiths, the city was flooded by Ingward and two other healers to contain the threat of the Darkwraiths, despite the massive loss of life.
Despite the Four King's former loyalty to Gwyn, strangely no statues or other signs of worship of him can be found in New Londo, only Velka. This might imply that Velka had a hand in the Four Kings betraying Gwyn.
These haunted, dark and initially flooded ruins are located directly beneath Firelink Shrine and are haunted by cursed souls. After draining the water, the lower part will become accessible.
Rickert of Vinheim can be found here.
Design Works Interview
Theories
Title of theory
Sources
PREV: Lost Izalith
NEXT: Northern Undead Asylum