Stunning Roman aqueduct used for 1900 years and still standing.

Long tunnels run under the ancient chariot racing circuit to the tower.

This foreboding medieval castle was twice besieged by barons rebelling against the English king.

A spectacular hidden beach in Ireland has the dark, disturbing nickname of "Murder Hole Beach."

A scattered trail of street art adds a pop of color to the city's stark structures.

This Italian-style temple replica has been threatening to fall off the Irish coast for hundreds of years.

This short bridge is the only thing connecting a tiny Irish island to the mainland.

Northern Ireland's Brobdingnagian stepping stones.

This World War II relic let Allied pilots know they were entering neutral airspace.

A retired military stronghold on the rolling green coast of Donegal.

An abandoned faux-pub made famous by a Guinness commercial.

This small Irish village suffered the greatest loss of life when the Titanic sank.

Ireland's most remarkable collection of these curious cone-shaped houses is worth the buzz.

You can see three Irish counties from this Neolithic hillside fort, once the seat of the Kingdom of Ailech.

The 19th-century pharmacy (now a used bookstore) was featured in James Joyce’s "Ulysses," and has changed very little to this day.

This single room has survived the centuries with almost no deterioration.

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.