Ancient civilizations

The Arch of Constantine, next to the Colosseum in Rome, was dedicated to Emperor Constantine in AD 315.

Trajan's Markets in Rome is often called the world's oldest shopping mall.

The Pont du Gard, the Roman aqueduct bridge near Nîmes in southern France, is covered in stones sticking out of its piers and arches.

China's first emperor, Qin Shi Huang (died 210 BC), lies under a tree-covered mound near Xi'an that has never been opened.

How did the Colosseum, a stadium built for public killing in ancient Rome, survive almost 2,000 years?

Every visitor enters the Great Pyramid of Giza through a robbers' hole.

People still live in flats on top of Rome's Theatre of Marcellus, a Roman theatre finished in 13 BC.

The Appian Way, Rome's first great highway, was begun in 312 BC, and cars still drive on part of it today.

The Trevi Fountain is the end point of the Aqua Virgo, a Roman aqueduct finished by Agrippa in 19 BC that still carries water into Rome.

Hagia Sophia was the biggest church on Earth and went up in under six years, and that haste is part of why its first dome fell in 558.

The best view of Trajan's Column isn't in Rome.

Every visitor who goes inside the Great Pyramid of Giza walks in through the Robbers' Tunnel, a rough hole forced into the north face below Khufu's real entrance.

The Gulf sits beside the largest sand sea on Earth, but wind-polished dune sand makes weak concrete, so the UAE still imports millions of tonnes of sand.

The Pons Fabricius in Rome, built in 62 BC, is the oldest Roman bridge in the city still standing in its original form, and it still carries its builder's inscription.

In World War I, Britain painted thousands of ships in clashing "dazzle" patterns.

From the air, lines of holes across Iran's deserts look like craters.

Ming-dynasty builders boiled sticky rice into a thin soup and mixed it into lime mortar.

These stone steps near Arles, in southern France, are what's left of the Barbegal mills: a Roman water-powered factory built around 120 to 130 AD.

More than half of the Colosseum's outer wall is missing, and it wasn't bombs or weather.

The Great Sphinx of Giza lost its nose long before Napoleon reached Egypt in 1798.

A painting in the tomb of Djehutihotep (El-Bersheh, Egypt, c.

When Mount Vesuvius erupted in AD 79, a building crew in Pompeii left a wall half-finished, with piles of raw materials still on site.

Those holes all over the Colosseum are not battle damage.

King Tut’s dagger was made from meteorite iron.

Pliny the Elder claimed Roman harbor concrete got "every day stronger" under the sea.

The Great Pyramid was built white: smooth, polished limestone from base to tip, and about eight metres taller than it is today.

Machu Picchu’s terraces hide an extensive drainage system.

Two miles from Stonehenge, around 2500 BC, people raised rings of timber posts now called Woodhenge, lined up on the midsummer sunrise like Stonehenge.

Ice in a desert summer had a winter supply chain.

Rust helped protect Delhi’s iron pillar for roughly 1,600 years.

Those rough blocks were never meant to be the Great Pyramid’s finished surface.

Rome's Pantheon, finished around 125 AD, still holds the record for the world's largest unreinforced concrete dome, nearly 1,900 years later.

A cold drink in Calcutta could contain ice shipped from another continent.

The ancient Greeks built the Diolkos, a paved stone trackway across the Isthmus of Corinth, and hauled ships overland on it for centuries; a canal across the Isthmus was attempted by Nero in AD 67 and not completed until 1893.

Honey essentially never spoils: its very low moisture, high acidity, and natural hydrogen peroxide make it inhospitable to microbes, and archaeologists have reported edible 3,000-year-old honey from ancient Egyptian tombs.

The ancient Romans used a concrete called opus caementicium that contained seawater and volcanic ash (pozzolana), and marine structures built with it have been found to be stronger after 2,000 years of seawater exposure than when they were first poured, because seawater triggers the continued growth of a rare mineral called tobermorite within the concrete.