Trails through lava-carved tube-caves display sparkling bacteria and a rich history.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

Towering basalt columns, a creation of fire and ice.

Olfactory delights in San Francisco's Botanical Gardens.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

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

No one knows who created the statues or if they are arranged properly—let alone the artwork's real name.

No shoes allowed on this trail, which is designed to be experienced barefoot.

A trash dump made beautiful by nature's power.

Cliffs full of fossils at the portal to England's Jurassic Coast.

Tracks near this Texas nature site were once thought to support the Creationist belief that man and dino coexisted.

A trough of 700 strange bronze faces runs through a narrow alley in Ljubljana's old town.

Believed to have once stored either human remains or rice wine, thousands of mysterious stone jars lie in ruin.

A 15-foot-tall statue of the head of the Sopranos family greets passengers at a train station in southeastern Lithuania.

When construction began on this hotel, developers were surprised to find the ruins of an ancient civilization.

A 30-acre garden inspired by the principles of modern physics.

This Costa Rican topiary park is a surreal garden of unearthly delights.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

Visitors can walk over the largest concentration of Columbian mammoths to have died from one event.

This beautiful grotto is one of those places where you can't believe you're just outside Austin.

An emerald-green grotto just a short trip from Austin.

Western Europe's only representation of a Roman goddess still in its original location sits in an unassuming park.

This one-of-a-kind archeological site is home to strange prehistoric ruins, the original use of which is still a mystery.