This 11th-century castle sits so low you can't see it behind the surrounding buildings.

The remains of a medieval wall discovered in the basement of a jewelry store.

An unassuming rod in the Netherlands was once the old standard unit of length for the entire Dutch empire.

A trio of red, white, and blue stones embedded in the streets of Leiden are markers of medieval territory and law.

People have been placing babies on these lilies for photoshoots since the Victorian era.

The grave of the famous painter is marked by a simple stone in the ground.

Amsterdam's former hotspot for public executions and dissections.

One of Amsterdam's narrowest houses is located right across the canal from its widest.

The former headquarters of history's oldest megacorporation.

Lumps of significant stone from around the world surround a flaming monument for peace.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

A set of seven houses, each built in a style that represents a European country.

This plaque marks the former home of one of the first women physicians in the Netherlands.

This unattributed sculpture in Amsterdam is hiding in plain sight.

A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.

In the days before house numbers, these colorful signs held clues about various buildings' purposes.

A pocket of jungle amidst urban expansion in Panama.

This church was transported brick by brick from the ruins of a 16th-century city into Panama City's current historic district.

The wooden airship was the largest flying boat ever built.

This 85-foot-long table is made from a single slice of an old-growth Douglas Fir.

The trunks of 3,000 year-old trees lurk beneath the surface of this crystal clear lake in Oregon.

Rushing water plunges over a 100-foot drop created by an ancient lava flow at this majestic waterfall.