Sometimes the earth reveals them voluntarily, sometimes they are found by chance and often they are searched for - archaeological riches. Excavation sites around the world offer fascinating insights into the origins of our cultures.

Farmers came across a clay figure while working near Xi'an in 1974. Their discovery was a sensation. They had stumbled upon the mausoleum of the first emperor of China: Qin Shihuangdi, who died in 210 BC. Since then, thousands of life-size terracotta soldiers have guarded the tomb of the ruler. With about 100 square kilometers, the imperial tomb is the largest excavation site in the world.

240 kilometers (149 miles) northwest of the capital Phnom Penh, in the middle of the jungle, lies the enchanted temple complex of Angkor Wat - part of a medieval city of millions, ornately built from sandstone. 150 years ago the French colonial rulers discovered the sunken empire of the Khmer, who once lived here. The stone reliefs on the temple walls tell their story.

The old Inca town of Machu Picchu was once only accessible on foot via a steep path. It is situated 2,360 meters (7743 ft.) up in the Andes. Not even the Spanish conquerors advanced to this point. The terraced city was only discovered about one hundred years ago. Built in the 15th century, it is regarded as an impressive example of the high culture of the Incas.

3000 years ago the Maya founded settlements all over Central America. Especially on the Yucatán peninsula in Mexico. Uxmal is considered one of the best preserved Mayan sites. In the center of the city: the Pyramid of the Magician, 38 meters (125 ft.) high. This Mayan sanctuary took 300 years to build. As tempting as it is, you are not however allowed to climb up it.

The eruption of Vesuvius in the Gulf of Naples in 79 AD was devastating. The ash rain buried the city of Pompeii and its inhabitants. After their corpses had decomposed, cavities remained, which were later filled with plaster by conservationists. The plastic plaster casts of people in mortal fear leave no visitor to the excavation site untouched.

German archaeologist Heinrich Schliemann was obsessed with Troy. At the end of the 19th century he began digging in the Turkish province of Çanakkale. His guide was the Iliad, the account of the Trojan War by the Greek philosopher Homer. Schliemann actually found a settlement. An important center of the Bronze Age, but whether it is actually Troy remains unclear to this day.

When you hear Delphi, you immediately think of the oracle of Delphi. The city was founded in the 7th century B.C. and was the center of the world for the people of antiquity. A place of pilgrimage for kings and all who sought advice. It was given to them in the temple of Apollo, by the priestess Pythia - the oracle of Delphi.

Researchers suspect that almost 2000 ancient cities are located on the territory of the former Roman Empire. Every Roman settlement had a center with temples, administrative buildings, shops and public squares - the so-called Forum. The Forum Romanum was more than that, it was the center of the entire Roman Empire. It is still one of the most important excavation sites of ancient Rome.

They are located near Cairo and are over 4,500 years old. Built as tombs for the Pharaohs Menkaure, Khafre (Chephren) and Khufu (Cheops) (from left to right), after whom they are also named. Although researchers have examined the inside of the pyramids with the most modern technology, the hidden chambers and galleries still keep their thousand-year-old secrets to this day.

First you pass through a narrow gorge, then you can see monumental temples carved into the rock. Many caravan routes led through the capital of the Nabataeans, which had its heyday as a trading center from the 5th to the 3rd century BC. T.E. Lawrence aka Lawrence of Arabia raved about Petra as "the most wonderful place in the world". To this day, the desert city enchants its visitors.

Deer, aurochs and horses - these are the best preserved prehistoric paintings in Europe, discovered in 1940 in a cave near Montignac. They are said to have originated 17,000 years BC. The cave is now closed for conservation reasons. However, visitors can admire the works of art by their ancestors in a perfect reproduction of the cave.

The megaliths near Salisbury date from the Neolithic Age and are probably the most famous stone circle in the world. Their purpose remains a mystery: cult site, temple complex, observatory? Some stones are aligned with the summer solstice. At the equinox of the day and night, thousands of people still celebrate the sunrise in this mythical place.

This place radiates a magical energy to many. It is still unclear why people erected the structure some 4,500 years ago: Was it a temple, a coronation site or an observatory for the sun? Stonehenge continues to cast its spell, with tens of thousands of visitors making the pilgrimage to the site every year, especially for the winter solstice.

About 500 years before Stonehenge was even erected, people built the Ring of Brodgar on the Orkney Islands, around 3200 B.C. The site features a huge stone circle that is 104 meters in diameter. Today, 27 of the original 60 boulders are still standing. Did these ancient builders later export their knowledge to Stonehenge? And was this ring also used as an astrological facility? No one knows.

These megaliths were also placed on one of the Orkney Islands around 3100 B.C. Archaeologist Nick Card believes that this was "an important site" some 5,000 years ago. He and his team have been excavating sites on the islands for years, and have now reconstructed 20 houses that once stood there. Card believes that people did not live here permanently, but came to hold festivities together.

The Carnac stones are 7,000 years old and continue to fascinate people today. About 3,000 standing stones ranging from 0.5 to four meters in height have survived for centuries. It is said that even Caesar's legionaries were amazed by the structure that stretches out for four kilometers. Did they serve as a place of assembly? Or was this a place of pilgrimage? That remains a secret.

This complex near Kaseberga is often called "Sweden's Stonehenge." However, this constellation of stones is not actually a circle: 59 stone blocks are aligned here in the shape of a ship hull that is 67 meters long and 19 meters wide. Archaeologists assume that Ales Stenar served as an ancient burial place some 1,400 years ago. The site attracts about 700,000 visitors every year.

Near the Swedish village of Bohuslän, there are another 100 or so stone circles and graves that were first laid out during the Iron Age. From this burial ground, you get a broad view over the nearby North Sea. Researchers believe that the site was still in use as recently as the Middle Ages, as a meeting place.

These stone relics of an earlier culture were uncovered in the remote Katun Valley of Russia's Altai Mountains. Some of the rocks feature prehistoric engravings. Scientists suspect that this was a sacred place of worship, which — similarly to Stonehenge — was probably also used for astronomical purposes.

There are four stone circles in the middle of the forest near the German village of Boitin. According to a legend, a wedding took place here once upon a time. The party went a little out of hand, with the wedding guests treating their food without respect, throwing bread and sausages around in their merriment. The gods then turned them into rocks.

These six preserved megalithic tombs near Lüdelsen in Saxony-Anhalt date back to the Neolithic period. Together with about 50 other preserved megalithic tombs in the region, there are plans to build a 40 kilometer-long "Megalith Route Altmark" to attract tourists.

Residents of Chile's Easter Island, which is located in the middle of the Pacific Ocean, call these statues Moai — which translates as "stone figure." Researchers date the 900 monuments back to between the years 1250 and 1500, and many assume that they represented chiefs or ancestors, who were believed to act as a link between this world and the next.