This world is basically a huge vertical cliff wall, hundreds of kilometers high. Some of the crevices and ledges in that wall are large enough to build cities on (up to kilometers in length and up to 500 meters wide). That's the largest horizontal surfaces available in this world, the chasm is literally bottomless.
How can such a world have cultivable soil on those ledges and crevices that can have things growing in it like trees or crops, if by logic erosion by wind and water from rains should flush everything off the cliffs into Below (which is inhospitably dangerous to all life even if there is a normal flat land somewhere down there)?
The technology level is somewhere around the late 19th century. No magic. Explanations that propose natural solutions are highly desirable over artificial means, since the people should've been able to survive and have agriculture in these conditions before inventing these artificial means to create and retain soil.