The glowing blue Nymphaeum of Emperor Tiberius.

The largest earthwork effigy in the world.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

More gold than anywhere else, ever.

The site of one of history's most indelible and horrific tragedies.

Earth's tallest volcano is sacred to Native Hawaiians, and home to a dozen world-class observatories.

The world's tallest doric column is this Ohio monument to a naval victory in the War of 1812.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

Bat house that has only ever housed bat for one night; they all flew away and never came back.

A modern addition to the Greenpoint skyline.

High on a hill overlooking Los Angeles lives a world famous, high-power conical Tesla Coil.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

The "dragon babies" of southeastern Europe.

Pilgrimage site for star-crossed lovers.

A marvel of Byzantine engineering under the streets of Istanbul.

The site of Paul Revere's historic two lantern warning.

The largest axe on the planet contains a time capsule that seems like it may never be discovered.

This modern museum of Mediterranean culture is surrounded by a surreal concrete honeycomb.

Empty, but not abandoned, this cavernous Brooklyn loading dock was once considered the largest individual building in the world.

The boulder on which Alexander Hamilton laid his head after a deadly duel can still be visited on the New Jersey coast.

The library of every book lover's dreams.

An odd, ancient window that may have once been part of a brutal prison is embedded in the side of New York's Police Plaza.

The remains of the furnace and iron works that produced the massive Hudson River Chain still stand in the woods of New York.

This huge, disused viaduct is now a crumbling concrete underworld of covered in years of graffiti.