This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

An architect's childhood fantasy treehouse made real.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

A beautiful geyser under environmental threat.

One man's ambition created this psychedelic log home.

The eerie ruins of this feudal fortress witnessed the execution of 60 conspirators in 1387.

The leathery remains of a woman who died in the 13th century now lie in a church named for her.

Plaques on its facade commemorate the Tiber's most destructive deluges.

One of ancient Etruria's most spectacular archaeological sites with impressive necropolises and rugged landscape.

Believed to be the remains of the lost Temple of Minerva, this nymphaeum has been known by its misnomer to this day.

The remains of this 2nd-century Roman temple are incorporated into a modern building.

This bustling Italian plaza is built on the ruins of an ancient Roman amphitheater.

A massive marble foot is tucked away in a small alley near the Pantheon.

Fortified medieval tower house with lovely roof garden.

This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

This is the oldest Roman-made bridge in the city still existing in its original state.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

Ancient ruins hidden underneath a modern luxury hotel.

The mystic whose incorrupt corpse still attracts the faithful.

A dismembered holy head stares out from her beautiful reliquary at the St. Dominic Basilica.

Renaissance hospital featuring a rotating door into which unwanted babies were dropped.