Sofia's legislative center is continuously reinventing itself.

A striking symbol of the Bulgarian capital.

This historic hotel invented the chocolate brownie.

A gothic church spire sits atop this skyscraper, the tallest church in the world.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.

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

This modern museum of Mediterranean culture is surrounded by a surreal concrete honeycomb.

This massive blockhead sculpture hides an entire library.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

It houses the remains of a 17th-century version of the Titanic.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

This curious, round temple is the oldest still-standing marble building in Rome.

This large, circular tomb is the final resting place of the first emperor of Rome.

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

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

A popular legend claims that the famous pizza was invented at a restaurant in this alley.

Every day is like Christmas on this street where the traditional Neapolitan nativity scene comes to life.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

Where members of the Crossbow Corps of San Marino demonstrate their skills.

The smaller of the three towers of San Marino is a former prison inaccessible from the ground level.

Legends surround an ancient tree trunk riddled with nails for good luck.

A silly medieval mural preserved on the side of a Viennese house.

Baroque celebration of the end of the Great Plague of Vienna.