This ex-prison dates back to the Middle Ages.

This quirky UFO-shaped curiosity is often mistaken for the airport’s control tower.

A chain of bells connect the California Missions and honor the legend of the "King’s Highway."

A massive volcanic plug is now a protected area that hosts a number of bird species.

A house built from trash known as the poor man's Hearst Castle.

This stretch of beach along California's central coast is a busy highway for the largest seal in the northern hemisphere.

The unbelievably opulent home built for an infamous newspaperman.

This one-block alleyway is stuffed with street art that is colorful, cultural, and intensely political.

A modern mechanical planetary system, part of a 10,000 year clock.

Once the fastest ship from San Francisco to Tahiti, the Galilee now lays in pieces in three different cities.

Visible below the waves are memorials to the city's Gold Rush dead.

An unassuming grey box sitting on San Francisco's Pier 17 is a "sky diary" of the coastal city's temperamental weather.

A glimpse into the lives of the the Miwok and Paiute people in Yosemite National Park.

The interior of the Overlook Hotel in "The Shining" was based on this Yosemite original.

A volcanic cone that formed over 600 years ago.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

This naturally heated mountainous creek has created a group of neon blue pools of potentially deadly boiling water.

Eons old volcanic activity created one of the most stunning rock formations in the United States.

This rock formation named for its unique shape is one of many that call the Alabama Hills home.

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

Las Vegas's very own 40-foot-tall fire-spewing praying mantis.

Europe's official "zero-level," the equator of elevation.

A beautifully eclectic mix of architectural styles.

Amsterdam's Red Light District leaves little to the imagination.