A daily replay of the experiment that proved the rotation of the Earth.

Yo, Adrian!

This elaborate towering structure was once famed for its revolutionary height.

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

An ancient knight and a symbol of the city's freedom.

A wunderkammer of gold and silver reliquaries and ancient saintly bones.

Built to bless whalers before their voyages, this Massachusetts church now features a ship-shaped pulpit.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

The American Revolution was galvanized into serious action due to the tragic clash with British soldiers that occurred at this location.

The U.S. Supreme Court's secret Cold War relocation facility in the mountains of North Carolina.

Infamous marsh filled with toxic waste, World War II-era London rubble, and dead mobsters galore.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

The "lovely red Vega" of the legendary record-settling pilot.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

This huge pile of volcanic boulders hides a stunning network of secret grottoes.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Every equinox this Maya pyramid puts on a spooky ancient light show.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

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

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

Carvings in Turkey's Marble Road may have directed ancient Romans to a hidden brothel.

A fountain standing as a testament to a doomed alliance.