An archaeologist in Bosnia claims to have found evidence of an advanced lost civilization in Europe that used impressive technology over 1,500 years ago. Controversial archaeologist Semir Osmanagic, also known as the “Bosnian Indiana Jones,” made the sensational claims after discovering a bizarre natural sphere near the town of Zavidovici in central Bosnia and Herzegovina. He believes it is the world’s oldest man-made sphere and the heaviest, weighing twice as much as the stone spheres of Costa Rica, which were created by the now extinct Diquis culture over 1,500 years ago.

While Osmanagic’s claims have been met with skepticism by some experts, he believes the sphere provides further proof of an advanced civilization with a high level of technology, about which we know very little. The archaeologist has been researching stone balls for 15 years and, based on visiting sites around the world, believes the ancient civilization used the stone ball in the belief that it attracted positive energy and was able to offer healing benefits.

The sphere has a radius of between four and five feet (1.2 to 1.5 meters) and an extremely high iron content, which Osmanagic believes may make it older than those in Costa Rica, as well as larger. However, a number of experts from the University of Manchester disagree and believe the boulder is not man-made.

Lecturer Mandy Edwards from the university’s School of Earth, Atmospheric and Environmental Sciences told MailOnline the spherical stone may be an example of concretion. This is when a compact mass of rock is formed by the precipitation of natural mineral cement within the spaces between sediment grains. The result is often spherical in shape, with the process forming the famed Koutu boulders in New Zealand.

Experts at the Geological Society said the round shape of the rock could be the result of like spheroidal weathering, a form of chemical weathering that affects jointed bedrock and results in the formation of concentric or spherical layers of highly decayed rock, and that there may be similar rocks in the area too.

Osmanagic has previously hit the headlines for his work on the supposed existence of ancient pyramids in the Visoko Valley, which he believes are hidden in plain sight as a cluster of hills. He believes once his research is complete, one of the pyramids will be shown to be taller than the Great Pyramid of Giza, Egypt. The Bosnian Prime Minister at the time, Nedzad Brankovic, backed his research, stating, “Why should we deny something that has attracted the attention of the whole world? We want to have official institutions involved in research in Visoko.”