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

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

A Nesting Doll of Churches.

2300-year-old Roman road connecting the empire.

The yawning maw of this pagan visage is said to bite off the hands of liars.

In 1329, Christine Carpenter entered this small stone cell in the hopes of becoming a living saint.

The ruins of an 800-year-old monastery boasts the tallest round tower in Ireland.

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

A particularly disconcerting tribute to Irish martyrs.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

Ancient rock-hewn town that witnessed key events of Georgian history.

The ruins of a town wiped out by the second-largest earthquake in recorded history.

The ruins of a medieval monastery named after a type of tree.

Mortarless walls that stretch for miles are a lovely solution for creating grazing land in the harsh terrain of the Aran Islands.

This ancient Irish tower could easily have stood in for Rapunzel's prison.

An ancient neolithic tomb that only sees the sun twice a year.

The ancient tomb acts as a calendar that keeps perfect time.

These gigantic skeletons tower over visitors and provide insight into the creatures that once ruled over Ireland.

Dublin's most modern, visually spectacular bridge is modeled after Ireland's national emblem.

Experience what life was like in Ireland during the Viking and medieval ages.

The mummified heart of a saint lives on in this church—after a brief hiatus when it was stolen.

Towering basalt columns, a creation of fire and ice.

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

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