This curious, round temple is the oldest still-standing marble building in Rome.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

Museum dedicated to literary greats of the Romantic Period is also the home in which Keats met his untimely end.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

The underground sanctuary of a mysterious ancient Roman religious cult contains an exquisite traditional fresco.

Eons ago, a rushing lava river formed this pristine passage through solid rock.

Ancient pueblos built into the base of a natural canyon wall.

A unique arch graces the Dolores River Canyon near the Hanging Flume.

This rugged area of red rocks and arches is often considered one of the most beautiful places on Earth.

This raised bulls-eye visible from space was the subject of an intense geologic controversy.

Few things look more out of place than the electric blue ponds in the reddish-brown desert of Utah.

It's safe—and permitted—to walk across these twin natural sandstone arches.

The cinder cone volcano with a less than complimentary name.

A crack flared at the base provides a pathway completely through a sandstone ridge near Moab.