Few other hotels can rival the grandeur of the Castle in the Rockies.

A walk through the historic city center, under the streets of Seattle.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Rock face that shares a name with Mary Shelley's famous doctor.

The once-abandoned 140-year-old hotel used in the movie "In Dreams."

The 340-year-old house that inspired the classic Nathaniel Hawthorne novel.

The only structure left with direct ties to the Salem witchcraft trials of 1692.

Why have you never heard of the second most popular tourist site in New York?

The world's largest kaleidoscope, designed by a 1960s psychedelic artist.

A mysterious air force base built to resemble a Long Island fishing village.

Want to build a wind turbine? Secede from the nation.

Try not to get slimed in Tribeca.

A large camera obscura, constructed entirely from digitally fabricated components.

Commemorating the spot where the famous scientist fed his pigeons.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

A celebration of capitalism in Midtown.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

Curious crustaceans support an obelisk from ancient Egypt that now stands in modern-day Central Park.

Visit the monolithic tomb of America's most famous general.

A curious fountain that has no water and includes Satan, a crab, and 9 giraffes.

A drawbridge named for a potentially intersex Polish national who fought alongside George Washington during the American Revolution, and an example of "Pulaski Red".

Mysterious 500-year-old tapestries depict a unicorn hunt.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.