A lovers' beach, tucked below the surface of the island, provides a safe haven for romance.

A Lovecraftian altar of nightmarish bronze chairs sits ominously on a boardwalk in Puerto Vallarta.

A giant Troll lurks under one of Seattle's oldest bridges.

A busy cafe better known for board games than food.

A walk through the historic city center, under the streets of Seattle.

A 100-year-old purveyor of curiosities, curios, and kitsch featuring mummies, shrunken heads, and a Fiji Mermaid.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Once the largest winery in the world, this castle-like building now sits abandoned on the San Pablo/San Francisco Bay shore.

The magic's in the hole!

Featuring a casually threatening atmosphere along with dessert and coffee to die for.

Beyond being incredibly fun, not much can be said about the Hole with certitude.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

The seamy, underground secrets of Portland's criminal past.

Shakespeare, David Bowie, Dr. Who, the Saxons, Druids and Romans are all claimed to have all made their mark on these massive man made tunnels.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

"The most colorful grottoes of the world.

Terrifically morbid cemetary and site of famous Paracelsus' grave.

No need to strap in for a "ride" on this walkable roller coaster.

The Bauhaus-style former industrial complex is considered the world's most beautiful coal mine.

Ancient man-made caves underneath small town Belgium.

Hiding the longest subterranean river known in the world.

Descend into the tunnels to experience the life of a coal miner.

A Belgian self-built tower inspired by the Bible and ancient civilizations.