Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Climb a set of vertiginous stone steps to the top of this impressive ancient edifice.

This column celebrates Rome's victory over the Goths, and may be the oldest Roman monument in Istanbul.

Ancient serpentine sacrifice holder that has stood the test of time.

Step back in time and witness the fall of Constantinople.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A marvel of Byzantine engineering under the streets of Istanbul.

An ancient Greek monument and a Byzantine church coexist inside this cave.

Legend says it was constructed with the destroyed pillar of an ancient Greek Temple.

A tiny Greek Orthodox church from the Ottoman era hides on a busy city street.

Gladiators once walked this ancient, subterranean passage.

These caves secretly held national treasures during World War II.

A man's head is enshrined beneath a statue near the first building constructed for the modern Olympic Games.

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

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

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

An ancient octagonal weather station named for the eight Greek gods of wind.

The railway carts travelers to central Athens's highest peak, which offers stunning vistas of the city.

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

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.