premise: At the northern edge of the district is Bozu Jigoku ( Monk's Hell ), an obscenely bubbling mud pond where a Buddhist temple once stood until it was submerged in an earthquake back in the 15th century.
hypothesis: Bozo Jigoku, or Monk's Hell, has sat at the northern part of the district ever since a Buddhist temple in the area was destroyed by an earthquake in the 15th century.