This ancient Spanish castle sits high upon a hilltop.

This funky former tobacco factory is one of the most striking examples of Madrid's cultural diversity.

A site where “the ravages of the war are more striking…than any other place in contemporary Spain.”

A Romanesque tower appears when water levels drop.

Partially collapsed lava tube and cave system complete with concert hall, underground pond, and unique albino crabs.

Stunning Roman aqueduct used for 1900 years and still standing.

The morbid items in this small and hidden museum are not for the weak stomached.

A whimsical brother of the nearby Fallen Angel statue takes the falling part quite literally.

This Funeral Hearse Museum represents the finest in cadaver transportation.

Turntable anonymously received orphans, alms, and groceries.

Hundreds of stone stairs and a winding medieval bridge connect this haunting Spanish island to the mainland.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

A modern Nordic Pompeii on the Icelandic island of Heimaey.

This tumultuous Icelandic lava field looks so alien European researchers want to use it as a stand-in for Mars.

An encyclopedic collection of mammal penises.

One time home to turn of the century explosives, now hidden under the Bay Bridge.

Chevron maintains one “Standard” brand station per state so it doesn’t lose the trademark.

The rustic cabin-like decor of this Arts and Crafts-style church reflects the love of nature central to its little-known theology.

A monumental cross hides in the trees in Golden Gate Park.

A masterpiece in Golden Gate Park by virtue of the artist’s debt.

A pair of mutilated bronze octopuses slump at the base of the monument honoring California's admission to the U.S.

One of few lasting examples of the brief octagon craze that developed into folly.

A speck of nature and art in one of San Francisco’s most notorious neighborhoods.

A man-made island in scenic San Francisco Bay.