Our planet is dotted with baffling monuments of unknown origin and purpose. Scientists have been racking their brains over these riddles for years, but the more answers they come up with, the more new questions arise. Let's explore some of the most inscrutable monuments scattered across the planet.

Stonehenge
© Flickr/ Alex RanaldiStonehenge
Legend has it that Stonehenge was erected by Merlin the wizard. But from the scientific perspective, the monument had emerged long before the life of King Arthur's wise companion. It is still unclear how people transported the monumental blocks from a quarry located hundreds of kilometers away. And what was the purpose of the structure? Was it an observatory (the megaliths form a precise model of the Solar System), a sanctuary (as it was used by druids) or something else?

Temple of Bacchus
© Flickr/ Caroline GranycomeTemple of Bacchus, Baalbek, Lebanon
The ancient-style temple complex is the pearl among the ruins of the once blossoming city of Baalbek in Lebanon. But the issue is that the Romans did not have technologies for installing blocks weighing up to 1,000 tons. Some believe the temple's basement was actually that of the Tower of Babel.

Newgrange
© Flickr/ young shanahanNewgrange
Road workers discovered Newgrange in the 17th century but scientists embarked on its exploration only some 300 years later. The burial mound was found to be older than the Pyramids in Egypt. If a person stands in the tomb on the days of winter and summer solstice, he or she can observe an amazing phenomenon of sunrays gradually filling up the room. The Irish believe that the place is a doorway to the realm of elfins.

Temple of the Grand Jaguar
© Flickr/ Bernard DupontTemple of the Grand Jaguar
The Temple of the Grand Jaguar is located in Tikal, an ancient Mayan city shrouded in jungle. Tikal bears the nickname "City of Voices", as even the slightest whisper there is loudly echoed by the city's pyramids.

Petrospheres
© AFP 2016/ Yuri Cortez
Over 300 petrospheres in Costa Rica had nearly fallen victim to workers who thought that gold was hidden inside of them. It is impossible to determine what those spheres symbolize, what kind of force manufactured them and when they were crafted.

Terracotta Army
© AFP 2016/ Frederic J. Brown / filesTerracotta Army
The mausoleum of Chinese emperor Qin Shi Huang musters over 8,000 statues of warriors and horses. They were buried together with their lord unconventionally - instead of real people and animals. The hand-made Terracotta Army dating back to 200 BC depicts the soldiers in full size. Moreover, the figures are detailed to the outmost degree, and you cannot see two identical faces there. An old legend about mercury rivers flowing around the buried emperor makes archeologists work very carefully there.

Angkor Wat
© Flickr/ Claudia SchillingerAngkor Wat
The Angkor Wat temple complex in Cambodia is regarded as the largest religious site in the world, covering an area of 162.6 hectares. The 200 temples are located in such a manner that strangers can see only three of them irrespective of the side they approach it.

Man near dessert mosque
© AFP 2016/ Sebastien RieussecA man stands in front of the Djingareyber mosque on February 4, 2016 in Timbuktu, central Mali.
French explorer Rene Caillie was the first European who returned alive from the town of Timbuktu in Mali, disguised as a pilgrim. The city is famous for its unique earthen architecture.

Easter Island
© Flickr/ David BerkowitzEaster Island
Easter Island is a tiny land mass in the Pacific Ocean dotted with Moai monolithic figures. Unfortunately, the people, whose descendants could shed light on the history of the mysterious statues, had died because of slavery.

Sphinx
© Flickr/ Sam valadiThe Sphinx
The colossal sculpture of the Great Sphinx of Giza in Egypt is the greatest riddle. Standing as a sentry to the desert, the Sphinx is attributed to the Biblical Flood and Atlantis. Secret rooms were found in the monument but accidents and political squabbles have barred scientists from unraveling the mysteries of the Sphinx.