The scuba diving training facility was named for the steam that rises from the cave's chimney.

An underwater city for the dead.

The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

San Francisco's newly reopened hands-on science museum.

Home to items never before seen by the public.

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

The magic's in the hole!

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

Famously misunderstood wonder of the ancient world

A museum dedicated to the history and exploration of both popular music and science fiction.

Elevated freight railway turned wildly successful urban park.

The Andean town where every single building is decorated with a brightly colored frieze.

It is said the legendary wizard once lived in this sea cave beneath Tintagel Castle.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

The original vault that held the president's remains still stands, empty, not far from where he was finally buried.

This odd stone memorial remembers a loyal dog who offended the rail barons with his speed and saved his master with his pee.

This wooded grove of beautiful hand-built stone grottos is a hidden gem within a shuttered Franciscan monastery.

A creepy sculpture of a decapitated head invites viewers to see St. Louis through its empty eyes.

A goddess-topped water fountain in Chicago was created thanks to the dreams of a thirsty newsboy.

The iconic Chicago sculpture hides a beautiful and easily overlooked plaque on the backside.