The 1.7-acre landmark overlooking the San Diego Bay was built for fast-food mogul Robert O. Petersen and just hit the market ...

The mansion boasts a 40,000-square-foot home, an underground tunnel connecting to an unfinished 20,000-square-foot pool barn, and an underground raceway.

It's a 40,000-square-foot home with an underground tunnel connecting it to the unfinished 20,000-square-foot pool barn, ...

In this full video, we reveal the entire process of building the most awesome secret underground mansion, complete with a ...