Answer:
I build up castles. I tear down mountains. I make some men blind, but I help others to see. What am I?
What two keys cannot open any door?
I have a small hill with seven holes. What am I?
I march before armies, a thousand salute me. My fall can bring victory, but no one would shoot me. What am I?
What is so delicate that saying its name breaks it?
They are many and one, they wave and they drum, Used to cover a state, they go with you everywhere.