This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

A Byzantine church containing the holy remnants of three saints sits atop the site of an ancient temple.

The only surviving choragic monument is a trophy awarded in 334 BC for the winning dramatic chorus.

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

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

Gladiators once walked this ancient, subterranean passage.

A sharp sculpture made of thousands of pieces of jagged glass.

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

One of the most photographed locations in the entire city.

A little-known park with unusual, half-ruined structures and a mystical energy.

An abandoned Byzantine fortress and notorious prison.

Byzantine emperors ruled, lived, and died in this 13th-century palace-turned-museum.

The most metal church of all time was built in record time because of an international, pious pissing contest.

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

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

A fountain standing as a testament to a doomed alliance.

A marvel of Byzantine engineering under the streets of Istanbul.

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

The legendary luxury train passage is commemorated with a charming museum inside its former eastern terminus.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

One of the newest mosques in a city filled with thousands.

"Holy Wisdom" overlooks the city that became its namesake.

Sofia's legislative center is continuously reinventing itself.

This building has two facades of clashing architectural designs.