One of the largest underground systems runs under Canada's largest urban center.

This narrow coastline trail through the dense Kauai wilderness is among the most beautiful and dangerous in the world.

This former luxury resort in Kaua'i is now an abandoned relic.

This blowhole is supposedly caused by a trapped monster.

This Hawaiian cattle ranch acts as a museum devoted to the island cowboys that predate the wild west.

This unusual lava tube spouts seawater during high surf.

California's oldest existing theater building hosted an impressive cast of celebrities, including hosting Mark Twain's first lecture.

Hidden in a hotel parking lot is a strange historical plaque erected by an obscure fraternal society.

The Empire Mine is "one of the oldest, largest, deepest, longest and richest gold mines in California."

Dentist's hated concrete colossi are now beloved icons of the community.

This former boomtown "island" is now submerged below Folsom Lake.

This 19th century hydroelectric powerhouse was the first of its kind.

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.