What am I?

I build up castles. I tear down mountains. I make some men blind, I help others to see. What am I?

related riddles

Where force can't get through, I with a gentle movement do. What am I?

Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls. What am I?

I am a vegetable that bugs stay away from. What am I?