The only Bahá'í house of worship in North America and one of only a handful worldwide.

This historic hotel invented the chocolate brownie.

The castle still holds traces of the abandoned Roman fort it was built atop.

This castle has links to Portugal’s founding and struggles for independence.

This giant sculpture made of trash is a critique of society's wastefulness.

Elaborate tile work in this railway station tells the story of Portugal.

A stunning 18th-century site where pilgrims ascend by a series of punishing stairs only to return via funicular.

A hidden three-foot-wide house separates these two regal churches.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

Bits and pieces from the ill-fated Donner Party's winter cabins.

Once at the center of U.S. finance, the historic Trading Room was meticulously recreated piece by piece and rebuilt in the Art Institute.

Fragments of architectural wonders from around the globe are embedded in the newspaper building's walls.

One of the oldest scientific gardens in Britain, containing more than 13,302 plant species in its core collection.

Famously misunderstood wonder of the ancient world

Dedicated to the art and science of glass in equal measure, this space is as much laboratory as museum.

Legend says this sacred tree was a gift from goddess Athena.

This monument is dedicated to a young boy who survived a disaster that forced Edinburgh to reevaluate its building codes.

Edinburgh's oldest statue hides within a parking lot behind the city's iconic cathedral.

Brass bricks outline the locations of Edinburgh's lost, lively market stalls.

The Scottish Reformation leader's grave was paved over and is now a parking lot.

Overlooking the burial ground is a tower designed to prevent thieves from snatching the recently deceased.

Touching this 18th-century Scottish philosopher’s toe allegedly conjures good fortune.

Now home to a drinking establishment, this building has a macabre history.

Remnants of the 16th-century defensive wall still stand unassumingly within Edinburgh.