Breathtaking and huge 430 year old maps of Italy.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

Catacombs turned marketplace.

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

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

This unreal Portuguese palace looks as though it's made from a pile of different castles.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

The glowing blue Nymphaeum of Emperor Tiberius.

Dublin's most modern, visually spectacular bridge is modeled after Ireland's national emblem.

One of Ireland's most infamous prisons for rebels including men, women and children.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

Medicinal spa created with the discharge from a geothermal energy plant.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.

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.

Macabre astrological automaton clock dating to the late 1400s.

The design of the Palacio Salvo has been described as "a lighthouse on top of a building."

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

A bright little alley in La Boca is a part of tango history.