In a 345-million-year-old cave that's 200 feet underground, dinner awaits.

What was once believed to be a church floor turned out to be the artwork of geology.

This unique structure allowed boats to bypass underwater mine barriers in the channel to enter the harbor.

This public observatory is home to the "celestial cannon," the longest pointable telescope in the world.

Nine of the very few concrete ships ever made in the U.S. are beautifully decaying off a Virginia pier.

Smoked mummies housed in mountainside caves.

A dark, narrow tunnel that leads to a charming lake and waterfall.

Located more than 600 feet beneath sea level, this tunnel boasts the world's first undersea roundabout.

The ominously named cave is home to some remarkable ancient art.

Some call this eerie forest of crooked trees the "Bermuda Triangle of Romania."

This Hungarian stilt village is built in a lake that never freezes over due to the power plant that that uses it as a cooling pond.

The site of an early Arthurian battle and the dwelling-place of prehistoric people and (possibly) an ancient race of giants.

Local stories say that if you drink from this well, you will return to Olympia.

This seaside property, an example of Art Deco Streamline Moderne style, was designed to embody the curves of a great ship.

During World War II, Austria's oldest salt mine was used to store thousands of pieces of stolen artwork.

Mounds of fine golden sand that can rise nearly 500 feet tall.

An underground world of gorgeous, palatial metro stations designed as a nuclear shelter complex.

This Connecticut ferry has been operating in some form since 1655.

Hues of distinctive blue to bluish-green color the slopes of these hills.

Sit at the "Disney table,” where Walt and his team of "imagineers" once dined on the regular.

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

An unusual slot canyon in the Aztec/Navajo Sandstone has a cross-section like an inverted old-fashioned keyhole.

This massive subterranean fissure is known as the "underground Grand Canyon."

This massive underground salt mine now holds a sci-fi theme park in its depths.