Answer:
A house of wood in a hidden place. Built without nails or glue. High above the earthen ground It holds pale gems of blue.
Sometimes black, sometimes white, I have veins but no blood
I am always in front of you, but you will never see me. What am I?
I run around the city, but I never move.
What looks back but cannot see?
What is so fragile that saying its name breaks it?