No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

The ghostly remains of an accidental sea.

Standing in a state of "arrested decay," this ghost town allows for a detailed peek into Gold Rush life in an unusually harsh climate.

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

The haunting ruins of Jack London's dream house.

The former Naval shipyard is open for exploring - mostly.

The century-old bell and clock tower at UC Berkeley is the third-tallest in the world, and has fossils.

A shape-shifting buy-sell-trade bookstore, born to Beatnik Era spirit.

Handmade treasures from around the world.

An amazing collection of fantastic reptiles, amphibians, spiders, and insects.

A store that sells all manner of bones, insects, and animal curiosities.

A living time capsule of the 1960s Richardson Bay water-front.

Only hotel where you can legally launder money.

Early prototype for Frank Lloyd Wright's Guggenheim.

These WWII-era murals were initially booed as a libelous portrayal of the American dream but have survived multiple attempts to have them destroyed.

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

Nestled in the heart of San Francisco’s bustling Financial District stands a unique homage to the Mayan and Beaux Arts.

Depicting scenes of everyday life - and specific individuals - in Great Depression era San Francisco.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

San Francisco's first World's Fair, dedicated to the wonders of California.

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

San Francisco’s condensed garden of incredible plant growth.

Once the largest windmill outside of Holland, with enormous 114 foot sails.