The walls of the iconic dome are hollow and have a secret stairway.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Bar full of oddities, specimens, artifacts and homages to the great dime museums of the past.

The impeccably spiced roast pork buns at this bakery are worth the wait.

This unique sculpture proved invaluable when it saved a train from careening off the tracks.

This Luxembourg cave is covered in cryptic looking marks left by mining activity.

This tri-part waterfall is a little bit of fairytale beauty in the heart of Luxembourg's Little Switzerland.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

These unusual houses look like giant boats that washed ashore on a residential street.

An unusual slot canyon in the Aztec/Navajo Sandstone has a cross-section like an inverted old-fashioned keyhole.

A 90-ton, gravity-defiant steam locomotive shoots for the skies in this bizarrely beautiful public artwork.

A striking public sculpture representing the period of martial law in Communist Poland.

The silly symbol for an underground protest group is now scattered around the city.

A collection of old neon signs from all over Poland line a secluded courtyard.

Dedicated to the man who saved hundreds of children from Nazi-occupied Czechoslovakia.

A half-buried vehicle in Prague's is the latest iteration in a long-running piece by Czech artist David Černý.

The rusted creatures wait to be discovered in Prague's botanical garden.

A controversial artwork draws attention to the dark history of Prague's "Suicide Bridge."

A giant interactive periodic table with real samples of the elements.

One of the famous Czech artist's lesser-known Prague installations appears to be a glowing fetus affixed to a drainpipe.

Bullet holes in the church wall are a reminder of the violence that followed the assassination of a high-ranking Nazi officer.

Monument to a suicide protesting the Soviet invasion.