Classical ruins that remember ancient Rome's presence in Africa.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

Mausoleum and Holy Seat of Antiochus I of Commagene.

The ancient abodes are a testament to human ingenuity amid harsh climates.

This 18th-century complex has served as a mosque, mausoleum, and one of the largest caravanserais in India.

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

The ruins of a monastery that dates to the 7th century.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

A hugely vast Irish landscape of barren rock that stretches for miles.

This Neolithic passage tomb forms part of a World Heritage Site.

A Maori village obliterated by an 1886 volcanic eruption.

An ancient neolithic tomb that only sees the sun twice a year.

The highest point in Maine is a grand gift to the state citizens that also happens to be one end of the Appalachian Trail.

The historic cave is both a symbol of superstition and black magic and inspired one of the early Christian converts in Botswana.

Wondrous stalactites house thousands of bats in these African caves.

One of only two civilian settlements in the desolate lands of chilly Antarctica.

On the wall of this medieval square, a symbol of the Spanish Inquisition.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

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

The site of the earliest colonial settlement in the Bahamas started as a place of religious refuge.

A paradise hotel turned from opulent to overgrown.

Inhospitable caverns just beneath this island paradise offer insights into alien worlds.

This isthmus in the Bahamas narrowly separates the roiling Atlantic from the cool Bight of Eleuthera.

The world’s largest underwater sculpture is found just off the coast of Nassau.