A Civil War Museum with some notable medical antiques.

The 25th President's marble casket can be visited in this classical Ohio tomb.

The maritime museum that boasts the largest nautical library in the western hemisphere.

This historic cliffside mansion uses a natural cave for air conditioning.

Once connected to the outside world by a single train track, this ghost town is looked after by the National Park Service.

A bunker "with enough U.S. currency to replenish the cash supply east of the Mississippi" in the event of nuclear war now protects nitrate film.

"Dark Sky Park" is heaven on Earth for astronomers, one of the rare U.S. locations with no artificial light pollution.