Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

Site of a famous 19th-century transcendentalist utopian community, now abandoned.

A beautiful Victorian-era cemetery, complete with a miniature village.

America’s oldest community theater, this Boston club has been in operation since 1877.

Museum dedicated to awful artwork.

This vast, water-filled underground labyrinth can only be toured by boat.

This army of concretions is an unexplained geological phenomenon unlike anything else in the world.

The sunlight passing through the opening of this huge cave system creates a magical effect.

This cave system allegedly holds the "metallic library" of a lost ancient civilization.

These otherworldly caverns form Earth's oldest known cave system.

At the right time of day, sunlight floods through the roof of this cave and illuminates the small pavilion hidden within.

This amazing ancient cave was kept secret for seven years to protect it from the public.

This ancient cave is home to a museum, bar, and is filled with fluorescent minerals.

Perhaps the most spectacular grotto along the Algarve coastline.

Peek into a cave of giant, glimmering crystals.

The ceiling of this cavern is dripping with multicolored marble stalactites.

This ancient limestone cave system contains many impressive geological features.

One of few vertical lava tubes in the world accessible by foot.

The spectacular geological formations make it one of the most impressive caves in Europe.

A subterranean playground in an abandoned slate mine.

Legend has it these caves were created by a deity called Ogba, who is said to live inside the winding subterranean caverns.

Down-home Arkansas comfort food comes with a side of American pop culture kitsch.

A classic Route 66 landmark that was built with scrap lumber and is held together with kitsch and puns.

Prove you deserve to be fed by Kenny Shopsin.