The Outer wall is a barrier against the dangers from outside the city. In its shadows is another barrier, one from hope, comfort, and warmth.
Sky street (and the blocks around it) are odd. The shadows are darker. The air is damper. The mood is bleak and errie. The street is silent, all the noise muted somehow. However, you can always seem to hear someone crying.
Everyone has to live and work somewhere.
The street is wide, and smoothly paved, with trees planted along the sides. The houses are mansions and palaces, each surrounded by stone and ironwork walls that are as much decorative as they are protective. These are the summer homes of the Princesses, and ladies of privelage.
The PCs encounter an elaborate trap room, designed to fill with water, drowning those inside. Clever and resourceful, they disable the trap and move on.
Only later do they discover that this room is part of the elaborate cooling system that prevents beasts of elemental fire from overrunning the complex. While the fiery beasts run rampant, they begin setting fires, which causes the complex to become increasingly hot and smoke-filled. Additionally, the PCs now have to fight their way out past aggressive fire creatures...