These steeply terraced ruins are a stop along the Inca Trail to Machu Picchu.

The only visible reminders of an elaborate engineering project that kept the tower from reaching the tipping point.

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

A 16th-century Andalusian palace.

Water and windows define this defensive Italian well.

These gutted monastery ruins still stand proudly in the middle of the Italian countryside.

The world's largest wooden structure.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

Erotic art covers the walls of the largest ancient pleasure palace.

Eighty million natural history specimens call this gargantuan museum home.

This sword isn't waiting for a king to pull it out. It was placed there by a saint.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

Geothermal waterfalls in Tuscany.

Northern Ireland's Brobdingnagian stepping stones.

The atmospheric road was never meant to be so creepy.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

This ancient Irish religious site is covered in ancient carvings, many of which have barely aged.

Climb inside an iron crystal magnified 165 billion times its normal size.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

This elephant kraal is the only one remaining in Thailand, dating back to the 16th century when these massive mammals were integral players in war and trade.

A tall karst islet popularized by 007.

A 20-meter (65-foot) robot towers over Tokyo Bay.

A bronze statue dating back as far as 1252, still has remnants of gold on its right cheek from ancient gilding.

Nine Gardens in one—with tea service.