The world's largest frame offers spectacular views of the city's past and present.

A preposterously luxurious hotel with gold-plated iPads, Rolls Royce chauffeurs, and a staff that trains by watching "Downton Abbey."

This artificial archipelago was supposed to resemble a map of the world.

Finland's oldest astronomical observatory once played a crucial role in seafaring and timekeeping.

This irregularly shaped sea fortress has defended not one but three different sovereign states.

An abstract monument to a symphonic composer.

The underground sanctuary of a mysterious ancient cult.

The yawning maw of this pagan visage is said to bite off the hands of liars.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

In the Netherlands, one of the world's largest private car collections can be found.

The world's largest private telescope collection hides in a secret wing of a Dutch auto museum.

A miniature city, once ruled by the Queen of the Netherlands.

A seven-century-old jail tells a not-so-pleasant history of crime and punishment.