Difficult

Man walks over, and man swims under. In times of war, it can be burned asunder. What is it?

related riddles

A hole leading in, a hole leading out, we connect to a cavern that is slimy all throughout. What are we?

My first is second in line; I send shivers up your spine; not quite shining bright I glitter in the light.

What turns from red to black as soon as it touches water?