The Fallen City contains a large number of houses with narrow alleys and easily-accessible roofs - bodies of the past inhabitants, and possibly past Arisen and their respective Pawns, litter the streets. This underground city is located on top of a high plateau and one may fall off its edge if not careful.
Unless otherwise noted, items may be assumed to be obtainable at any time
It is possible to run through the city on the roof tops in order to avoid most of the enemies and quickly get to the Sanctum.
If the player stays in the Fallen City long enough, Death and a Cursed Dragon will continue to appear, alternating, one at a time.
The Wakestone will re-spawn every seven game days (Pre- and Post-Daimon).
Entering and exiting the Bitterblack Sanctum is necessary in order for the Fallen City chests to re-spawn in Pre-Daimon Bitterblack Isle.
If one reads Ashe's Account at the Monument of Remembrance, he describes his ruined village, furthermore Barroch states that the Arisen and he both wander about the imaginary world of your "host", which is, as Olra also states, Daimon. This is can be surmised that this area, The Fallen City, is indeed where Ashe was initially from as it is a portion (or recreated memory) of his ruined village afore he was made an Arisen.
Strider vs The Fallen City (full battle). No damage.
Hard mode demonstration with no armor, buffs, curatives or Wakestones used. The Arisen wields a Rusted Bow and Framae Daggers in order to debilitate and slay all enemies on the field. A Dragon's Ire bow is used to take out the 3 Living Armor at the end.
Mystic Knight vs The Fallen City (full battle). No damage.
Hard mode demonstration with no armor, buffs, curatives or Wakestones used. The Arisen wields a Magebreaker mace to freeze the Eliminators with its permanent Ice enchantment. A Rusted Staff is used to cast Ingle in order to lure the Living Armor out one at a time.