Eons ago, a rushing lava river formed this pristine passage through solid rock.

This serene oasis in an affluent Los Angeles neighborhood holds some of Gandhi's ashes and got Elvis into Eastern Philosophy.

A mysterious monument meant to be a guide into "an Age of Reason" was destroyed after an apparent bombing.

A historic neighborhood church is reborn as a psychedelic arts collective.

One man's vast collection of artifacts and ephemera from matchbooks and postcards to vintage neon signs and cars.

Become a prohibition rebel.

This futuristically sylvan church is a glass-enclosed marvel of modern architecture.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

It's not hard to see why the historic Peabody Conservatory of Music's library has been described as a "cathedral of books."

Left untouched since a double murder-suicide in the 1960s, Los Feliz murder mansion remains a neighborhood mystery.

An acoustic anomaly with a mysterious cause.

This natural wonder drops 16 stories straight down through rare flora and streaming waterfalls.

An underground mansion with fruit-bearing trees and grapes growing beneath the surface of central California.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

A library of rare occult books in Los Angeles.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

A dilapidated dock tells the story of Titanic's missed arrival.

The best place in the park to test out your throwing arm.

A New York garbage depot holds a secret collection of weird and wonderful refuse.

This abandoned amusement park was built on a site with a dark history.

The site of the climactic scene from the classic horror film is now a historic landmark.

The first declared National Monument in the United States.

A museum and shop on Bourbon Street located in the former home of the second Voodoo Queen of New Orleans.