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

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

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

Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

For decades, Puerta del Sol has been illuminated by a giant, guitar-wielding bottle of sherry.

An ancient Egyptian temple in the middle of Madrid, Spain.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

The world's largest wooden structure.

Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.

Eighty million natural history specimens call this gargantuan museum home.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

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

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

A marvel of Byzantine engineering under the streets of Istanbul.

Two stone columns flank the grand Venice square, but there were supposed to be three.

Da Vinci's equestrian statue, 500 years in the making.

Go inside to really appreciate this 500-year-old technological masterpiece.

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Museum celebrating the ocean, with the largest wunderkammer dedicated to sea exploration.

The celebrated eyesore created by starry-eyed sweethearts.

Lyon's miniature version of the Eiffel Tower was built as a statement in support of French secularism.

Trek up this glacier before it disappears.

A memorial to the nearly 10,000 American soldiers laid to rest on the beaches of Normandy during WWII.