Located in Turkey’s Anatolia region, the mysterious Göbekli Tepe consists of a series of rectangular rooms, stone circles and dozens of T-shaped limestone pillars, most of them carved with abstract symbols and pictures of menacing beasts such as scorpions, lions and snakes. The complex would be impressive in any era, but what makes it extraordinary is its extreme antiquity: it was built in the ninth or tenth millennium B.C., more than 6,500 years before the Great Pyramid of Giza and prior to the adoption of pottery, metal tools and even agriculture.

Many questions about Göbekli Tepe still remain unanswered, but archeologists believe it functioned as a religious site or ceremonial meeting place for its hunter-gatherer builders, which would make it the world’s oldest known temple.

The dazzling fortress city of Sigiriya is nestled around a rock outcropping on the Indian Ocean island of Sri Lanka. It was once the stronghold of King Kassapa I, an upstart monarch who usurped the throne in the fifth century A.D. and murdered his own father by entombing him inside a wall. Fearing a reprisal from his brother, Kassapa moved his court to the jungle and constructed a sumptuous new capital surrounded by landscaped gardens, fountains and pavilions. The city’s centerpiece was the “Lion’s Rock,” a 660-foot-tall granite plateau that was topped by the King’s pleasure palace.

The mountaintop citadel was accessed via a stairway guarded by a massive stone statue of a lion—only the paws of which remain today—and was adorned with terraced gardens, pools and elaborate frescoes of beautiful women. The sky palace served as Kassapa’s chief residence for several years, but his reign was later cut short in 495 A.D. when he committed suicide after his brother defeated him in battle. Following his death, the fortress at Sigiriya was converted into a Buddhist monastery.

The ancient mortuary temple known as the “Labyrinth” was allegedly built by the Egyptian pharaoh Amenemhat III in the 19th century B.C. and was housed at his pyramid complex at Hawara. The most detailed accounts of its design come from Greek and Roman writers, who described it as a maze-like, two-story structure filled with a dozen marble courts and thousands of individual chambers decorated with hieroglyphs and paintings. The different courts were connected by a series of winding passageways and corridors, which the historian Diodorus Siculus claimed were so bewildering that they could only be navigated with the help of a guide.

Almost no trace of the fabled Labyrinth survives today—it was likely broken up and plundered for other building projects—but if the ancient chroniclers are to be believed, it was once one of the great treasures of antiquity. Herodotus, for example, considered it “a work beyond words” that “surpasses even the pyramids.”

Built by King Ur-Nammu and his son Shulgi in the 21st century B.C., this sprawling step pyramid once served as the central religious and architectural monument of Ur, an ancient Sumerian metropolis located near the present-day city of Nasiriyah in Iraq. Like most ziggurats, it took the form of a terraced, mud-brick tower with successively receding levels. Its central feature was a series of monumental, 100-step staircases, which converged on an upper platform housing a shrine to the city-state’s patron deity, the moon god Nanna.

Only the bottom stages of the structure remain today, but in its heyday, the Great Ziggurat probably stood some 100 feet high and measured roughly 210 feet long and 150 feet wide. The site has undergone two major overhauls in its 4,000-year history. The first came in the sixth century B.C. when the Babylonian King Nabonidus repaired its decaying foundation and replaced its upper terraces. In the 1980s, meanwhile, the Iraqi leader Saddam Hussein restored its outer façade and completely rebuilt its three main staircases.

Longmen Grottoes is a collection of some 110,000 elegantly carved stone statues situated within 2,300 limestone caves in China’s Henan Province. The earliest pieces date to the fifth century A.D. and the Northern Wei Dynasty, but new works were still being added as recently as the 10th century thanks to commissions from emperors and wealthy individuals. The vast majority of the Longmen statues depict figures from the Buddhist religion.

The massive Fengxian cave includes a 55-foot tall carving of a seated Buddha flanked by eight disciples and heavenly guardians, while the Wan-fo-tung cave is home to 15,000 individual Buddha statues, some as little as 10 centimeters tall. Other grottoes feature ceremonial figures, imperial processions and some 2,800 inscriptions carved on stone steles. There is even a “Medical Prescription Cave” inscribed with more than 140 ancient medical treatments and cures for diseases.

In the lowland rainforests of Guatemala lie the ruins of Tikal, an ancient Mayan metropolis that flourished between the third and ninth centuries A.D. The city’s urban center boasts an array of footpaths, paved plazas and ball game courts as well as more than 3,000 different structures that rank among the best-preserved Mesoamerican monuments. These include several imposing step-pyramid temples, one of which rises above the jungle canopy to a height of 212 feet—possibly taller than any building in the Americas prior to the arrival of Columbus.

Another pyramid, known simply as Temple I, features nine levels of limestone blocks and contains the tomb of the Mayan ruler Jasaw Chan K’awiil I. As many as 70,000 people may have called Tikal home during the seventh and eighth centuries when it was one of the superpowers of the Mayan civilization, but it later underwent a mysterious decline before being abandoned sometime around 900 A.D. The city was then reclaimed by the jungle and was not rediscovered until 1848.

Often called “Ireland’s Stonehenge,” Newgrange is a dome-shaped, 249-foot-wide monument constructed around 3200 B.C. by the Neolithic inhabitants of what is now County Meath. A passage tomb, it features a 62-foot tunnel that gives way to a recessed central chamber containing stone basins filled with cremated bones. The site is renowned for its astronomical properties. Its ancient builders designed it so that every winter solstice—the shortest day of the year—the rising sun shines through a “roof box” near the entrance and floods the main passageway and the inner chamber with light.

While the tombs inside of Newgrange suggest that it served as a burial place for revered dead, the precise nature of its construction has led archaeologists to speculate that it also functioned as an important ritual site or even as a solar calendar to mark the beginning of the New Year. Whatever its original purpose, the mound eventually fell out of use and was abandoned for several millennia. It wasn’t rediscovered and unsealed until the late 17th century when a local landowner tried to dig up its foundation for use as construction materials.