An Iron Age fort on the edge of a seaside cliff offers a glimpse into an ancient, mystical world.

One of the most popular megalithic sites in Ireland stands as a humbler version of Stonehenge.

The ancient tomb acts as a calendar that keeps perfect time.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

This ancient Irish landscape boasts hundreds of legendary ruins.

These strikingly colorful paintings were created by a mysterious Mesoamerican civilization.

Underneath the historic center of Mexico City, the remains of a temple dedicated to the Aztec god of the wind.

Where a railroad loops under or over itself to rise or drop more than 70 feet in a short distance.

The peaceful gravesite of a rugged wild west gunman echoes the touching story of his last days.

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

This sculpture presents commentary on a life in pursuit of profits.

Mysterious lost empire of the Silk Road.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

Here, visitors can swing with the waves of the Pacific Ocean.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

This unique formation appears as though an asteroid landed on the forest.

A working model of the entire San Francisco Bay and much of the Sacramento River Delta, complete with regular tides that change every 14 minutes.

Discover for yourself what Herb Caen referred to as "the best kept secret in the Bay Area."

This infamous prison has a store where you can buy goods crafted by incarcerated people.

The fossilized remains of ancient California redwoods.

Neoclassical Revival mansion and set of horror cult classic Phantasm.

Eat a tasty meal in the house where John Steinbeck was born.

Over a century old, this restored Victorian building is surrounded by a lush garden filled with rare palms.

This teeny-tiny park built by a San Francisco man in 1962 is mostly stairs.