This ferry carries passengers across the Rhine propelled by no engine or paddles but by the river's current.

One of the world's largest collections of pharmaceutical artifacts.

An unassuming Swiss institution houses Europe's largest toy museum.

This artistic fountain display pays homage to this area's theatrical history.

This popular cave pool is truly magical, despite the crowds.

These winged Maya figures are the subject of speculation and conspiracies.

The ruins of a 16th-century Spanish convent tell a forgotten history.

If you can look past the nearby sewer pipes, this urban sinkhole grotto is a mini-paradise.

This small museum explores Mexican history and culture through clothing.

A cenote filled with Colonial era artifacts whose waters cannot be accessed.

These azure waters were thought to lead to the Mayan Underworld.

Found down a long dirt road, a sacred Mexican cenote and 18th-century hacienda remain hidden.

This one-of-a-kind convent boasts a kaleidoscopic exterior of stars and double-headed eagles.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

Every equinox this Maya pyramid puts on a spooky ancient light show.

A mysterious, abandoned Chinese building in Mexico pays homage to the area's East Asian immigrants.

Take a dip beneath the stalactites in this amazing cenote.

One of Mexico's youngest major cities still holds on to this structure representing its short modern history.

It might look like a doghouse, but this small structure was actually built to house a spirit from Maya mythology.

Few of the many visitors to this resort town know of its hidden Maya ruins.

This now-abandoned shopping center in Playa del Carmen was built to resemble a medieval European castle.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.