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

This massive redwood tree has a hole in the base big enough to drive through.

This rare example of a "tidefall" is a spectacular drop from the cliffs down onto the beach.

Once thought to be the oldest living tree in the world, Methuselah was germinated before the Egyptian pyramids were built.

A 300-ship graveyard, with a few still visible at low tide.

The site of murders and Satanic cult gatherings.

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

The ghost town that ended up on Ebay.

The "world's biggest dinosaur" once housed a creationist museum in its abdomen.

The lowest point in North America is home to an undrinkable pool surrounded by fields of geometric salt flats.

Small museum packed with artifacts recovered by the man rumored to be the real-life inspiration for Indiana Jones.

The remains of a ruined mansion memorialize the 1906 earthquake.

An extraordinarily ornate museum in San Diego holds wondrous anthropological treasures.

Nancy Thompson's Home from "A Nightmare on Elm Street."

The unbelievably opulent home built for an infamous newspaperman.

One of the ghostly stops along Route 66.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.

San Diego's most historic and haunted home.

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

Golden Gate Park's historic collection of plants.

A shrine to a skeleton saint in the city of angels.

San Francisco Bay's ghost town.

A volcanic tunnel illuminated by natural skylights offers a shaded respite from the desert sun.

A desert ghost town—occupied for only 12 years—was once home to more than 500 silver mines.