A natural dome made of volcanic glass in Inyo National Forest.

A volcanic cone that formed over 600 years ago.

Deep vertical fissures like miniature slot canyons cut across the cemented volcanic rock of Black Point above Mono Lake.

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

A new monument to an old grave that was uncovered during the rebuilding of a California ghost town.

A trompe-l'oeil statue honoring the first guide dog in North America.

Edison's cast-in-place concrete houses were a failure, but way ahead of their time.

This stunning Connecticut mansion is actually just a one-room-deep hoax.

The author of Uncle Tom's Cabin was neighbors with Mark Twain while living in this Connecticut home.

Thousands of American timepieces on display in the former clock-making capital of the country.

The former home of Samuel Clemens and family remembers the happiest period of the author's life.

Memorial to one of the most fatal fires in both circus and U.S. history.

This tiny church near Sleepy Hollow contains Henri Matisse's last work, a rose window, and nine windows by Marc Chagall.

The real-life site of Ichabod Crane's infamous gourd attack.

The home of one of America's most wealthy industrialists is now a historic site that remembers a more decadent time in the country's history.

Oldest existing church in New York and the inspiration for Washington Irving's "The Legend of Sleepy Hollow."

Elevated freight railway turned wildly successful urban park.

An artist's cute bronze subway sculptures belie his violent artistic past.

Cryptic messages embedded in the New York City sidewalk.

A semi-scholarly approach to sex.

The notorious headquarters of a corrupt political machine.

A hands-on traveling collection of the innovative devices of yesteryear.

The first piece of public art dedicated to LGBT rights.

Amid skyscrapers and traffic exists this unique aquatic ecosystem.