In the hinterlands of Serbia's capital, a giant reflective mushroom houses an aeronautical history of the former Yugoslav republic.

The interior of this Serbian royal family's mausoleum is covered with exquisite mosaics.

The palace for King Gustav III was never completed, but the foundation remains tucked away in this city park.

An exquisite Baroque church in Vienna's old town.

Legends surround an ancient tree trunk riddled with nails for good luck.

A huge wooden clock that is so beautiful its creator was forcibly blinded.

These rare statues are one of the few remaining material witnesses to Old Prussian culture.

This antique thermometer honors the creator of the first universal temperature scale.

A mysterious emblem tucked in an small alleyway is actually the coat of arms of a heroic medieval family.

Modern art commemorates one of the first military actions of World War II.

Memorial to the lost dead of Gdansk, whose resting places were destroyed during World War II.

The site of the first battle of World War II.

This Communist-era residential block is one of the longest residential building in Europe.

This fairytale inspired, warped building houses restaurants, shops, and a radio station.

The last living thing to come out of the rubble after 9/11 is now a symbol of hope and resilience.

A replica of a 7th-century church hides in plain sight in the middle of the concrete jungle.

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

Built hundreds of years ago this downtown iron barrier once protected a much despised king.

The most confusing clock in New York.

There must be a pun in this haystack somewhere...

Salute the leader of the proletariat.

Commemorating the spot where the famous scientist fed his pigeons.

A curious fountain that has no water and includes Satan, a crab, and 9 giraffes.

The oldest living tree in Manhattan comes shrouded in sinister legend.