This beautiful arched gate is all that remains of the fortress the ancient mountaintop town of Amadiya once was.

An ancient fortified mound raised over the millennia from settlements built one on top of the other.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

Brush shoulders with animatronic Arab leaders made of silicone.

This modernist cinema has survived war and reconstruction to become a symbol of Lebanon’s revolutionary spirit.

The ruins of an ancient Zoroastrian Tower of Silence believed to be the earliest example of the traditional funerary practice.

This "tower of death" has acted as an observatory, a religious hub, and an executioner's lair.

The only ancient site that remains on the south bank of the sacred Ilissos river.

A Byzantine church containing the holy remnants of three saints sits atop the site of an ancient temple.

A man's head is enshrined beneath a statue near the first building constructed for the modern Olympic Games.

This monumental work of art symbolizes the coming together of a previously divided city.

A slice of central Asia in the middle of Berlin.

Museum dedicated to the terror regimes of Hungary.

Two stunning 17th-century libraries and a cabinet of curiosities.

The quaint gallery displays works by artists from all across Mauritania.

The northernmost point in Denmark is a turbulent sandbar created by two clashing seas.

This Danish rock field is actually a sprawling ancient cemetery holding the bodies of 700 Vikings.

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

360° views of the city plus five floors of optical illusions and hands-on science.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.