A psychedelic labyrinth on the San Francisco bay.

An artsy hidden staircase leads to breathtaking views of San Francisco.

The world's only above water sand volcano, believed to once be the bathtub of a priest.

An untouched lava tube accessible to the adventurers.

One of Chile's most active volcanoes is riddled with beautiful caves.

A frozen oasis lies beneath the scorching New Mexico desert.

A historic coal mine that doubles as a museum and tourist attraction.

Home of a 28-foot tall stalagmite known as the War Club.

Spectacular mineral formations fill these caves, which have been used for everything from smoking meat to stashing illicit liquor.

This 18th-century folly is one of Europe's rare "garden mosques."

This bike path traverses the treetops.

This collection of solar timekeepers includes the world's first digital sundial.

This bike path was sunk below water level for maximum wonder.

A giant bug impaled on a 75-foot-tall needle.

This modern labyrinth lies in the shadow of a ruined medieval castle.

One of the largest Masonic temples in the world, created at the height of the oil boom in ostentatious style.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

The world’s largest Masonic temple was saved by the White Stripes.

Stumps of an Ice Age forest, visible only at low tide.

This 150 foot seven-tiered cascading waterfall is one of the hidden gems of the White Mountains.

Even Henry David Thoreau found this glacial pothole irresistible.

This narrow canyon has been carved by the river over thousands of years into spectacular and curious forms.

The highest peak in the state of Vermont has some interesting features.

This splendid Versailles-inspired mansion has the largest French-style formal gardens in North America.