This geothermal hot spring hides beneath a slowly growing mineral dome.

Site of the greatest known waterfall that ever existed.

A cave interior in the shape of the ancient rhinoceros, created by lava cooling around its carcass.

An exercise in patience and imagination, where Mother Earth turned common stuff into precious hidden treasures.

Cave carved out of a huge snow drift collapsed killing one and injuring five in July 2015.

The longest spit in the United States ends at a lighthouse in the Strait of Juan de Fuca.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

A crumbling hospital from the 1850s on Roosevelt Island.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

When it opened during the final years of the embargo, all the drinks and cigars were free.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

It's not hard to see why the historic Peabody Conservatory of Music's library has been described as a "cathedral of books."

Featuring Zürich's only authentic 14th-century plague doctor's uniform!

A 200-year-old tavern challenges guests to finish a glass of wine while hanging from a ceiling beam.

This basement museum explores the art and artistry of fascism.

Debatably clever, or just plain honest hotel advertised as "The Worst Hotel in the World."

A floating cat sanctuary on an Amsterdam canal.

A Portuguese Jewish cemetery filled with stunning grave monuments that date back to 1614.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.