A remarkable feat of Victorian engineering across the Firth of Forth.

This extinct volcano rises above Edinburgh and is special for its panoramic views over the city.

Looking strangely like Rome's Colosseum, this unfinished tower has dominated the skyline for over 100 years.

This site contains overlapping ancient graveyards that existed about 1,000 years apart.

This stately monument has been wearing a traffic cone hat for decades much to the delight of the locals.

This picturesque archeological site looks like it was pulled straight from a fantasy novel.

The remains of a grand castle that may have inspired Bram Stoker's Dracula.

The curios of pharmacist and collector Henry Wellcome.

A church of bones, decorated with 40,000 human skeletons.

One man's exploration of the human form, including the bizarre and delightful "Man Attacked by Babies."

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

A marvel of Byzantine engineering under the streets of Istanbul.

The first museum in the world devoted to sexual gadgetry.

Macabre astrological automaton clock dating to the late 1400s.

A collection of more than 12,000 shoes, displayed in a building shaped like a shoebox.

A 98-room castle in the middle of Toronto that bankrupted a 19th century electricity multimillionaire.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Mountain where Jesus was first tempted by the Devil.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

The attic of a four-century-old canal house hides a clandestine church.