He has set up an underground base on the Moon.

He didn't know we were there because the entrance to the underground base is covered by snow right now.

With the aim to research and explore techniques for building an underground base on the moon.

This underground base has recently been reported by several agencies, especially Indian ones.

Most especially if we could build a big mass driver to launch things from the underground base into orbit.

Travel from the underground base to the compound was usually by ground car.

It was a miniature of the one they had found in the American underground base.

You are to lead the raid on this underground base.

However, there were a third artillery, hidden in an underground base.