The National Park Service’s best-kept secret with views that rival any in D.C.

Look closely and you’ll notice that the color changes a third of the way up the tower.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

When it comes to handsignals (and colonialism) rock always beats scissors.

The most accurate timepiece in the world.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

The walls of America's oldest masonry fort famously "swallowed" cannonballs.

Former villa and estate of James Deering developed to preserve native tropical forests.

The castle where Martin Luther secretly translated the New Testament from Greek to German while in hiding.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

Nothing says indulgence like a 1,500-pound chocolate castle.

This Pennsylvania cave holds evidence of the oldest known inhabitants of North America.

Home to the deepest rift anywhere on Earth.

Supposedly Satanic numbers adorn this preserved submarine sail.

This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

The ruined doorway is a portal to the building's turbulent and torturous past.

This mystical orb covered in strange symbols is thought to have been used in ancient Greek magical rituals.

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

This black sand beach was crafted from volcanic explosions including the historic Minoan eruption.

This pink watchtower served as the seat of the Greek government after independence from the Turks.

Gladiators once walked this ancient, subterranean passage.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.