Rock-hewn monastery complex with hundreds of cave structures tucked away into the mountainside.

The charmingly disheveled clock tower of Tbilisi's puppet theater.

This Armenian monastery was carved out of cliffs and named after the spear used to stab Jesus.

Nestled in a peaceful valley, this Armenian monastery may have been saved from Mongols thanks to the eyes of God.

Giant stone letters dedicated to the founder of Armenia's alphabet.

A geological oddity topped with a 2,000-year-old pagan temple.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

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

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

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

Carvings in Turkey's Marble Road may have directed ancient Romans to a hidden brothel.

The ancient latrines of the Greeks, in all their public glory.

A marvel of Byzantine engineering under the streets of Istanbul.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

You will not be able to miss this building.

Go deep down into the earth to experience the world of Welsh coal miners.

One of England's most famous churches hides a pair of little known architectural treasures.

This former Welsh metal factory is now a lovely abandoned relic but was once one of the industry's world leaders.

The longest and tallest aqueduct in Britain can actually be sailed across.

Huge winged monument in the United Kingdom.

Gutted during the Liverpool Blitz, this architectural husk has been left destroyed in honor of the dead.

This well-preserved Cistercian Abbey in a romantic pastoral setting has inspired artists like the poet Wordsworth.

Recently restored menagerie of Victorian-era beasts.