Monasteries on rock pillars, once accessible only by frayed ropes.

Where commuters walk through remnants of an ancient Greek necropolis.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

Legend says this sacred tree was a gift from goddess Athena.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

Spain's largest bullring offers a unique glimpse at architecture and history.

The world's largest wooden structure.

Single runway interrupted by a busy road that cuts across its middle.

Whitewashed mosque contains the world's largest carpet.

This futuristic building is yet another architectural wonder in Dubai.

The world's largest frame offers spectacular views of the city's past and present.

On any given day this sprawling market houses literally tons of government-regulated gold, gems, and precious metals.

Op-art architecture designed for happiness.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

Eat the ultimate iteration of Portugal's most beloved pastry.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

The rusted creatures wait to be discovered in Prague's botanical garden.

A mocking tribute to the past and modern leadership of Prague.

A steampunk-styled three-floor factory churning out art, activism, and electronic beats.

Lonely minaret stump of a destroyed city.

This retro, UFO-like structure is a remnant of the Soviet-era circus.