In 2002, archaeologists found an unusual piece of round board in the pile-dwelling settlement of Stara Gmajna near Vrhnika, right next to Ljubljanica.
Research has shown that it is an exceptional find on a global scale. The object has been identified as a 5,200-year-old wheel with an axle. As such, it is the oldest dated wheel in the world and is listed on the UNESCO World Heritage Site. Given the quality of craft, experts believe that a top prehistoric wheel-maker made the wheel. The wheel was part of a two-wheeled cart and is as old as the Mesopotamian wheels. It is made of ash, wood and the axle is made of oak.
The Marshes wheel was preserved using the melamine method in which water is replaced by sugar. The process took two years; then, the wheel was dried for another two years. The wheel can be seen today in the City Museum of Ljubljana.