The Tolminka river bubbles to the surface in a delta-shaped karstic spring from beneath the mountains of Tolmin – Tolminski Migovec, Mahavšček, Tolminski Kuk and Rdeči rob. In its short, 10-km-long stream the river flows through a glacial mountain valley and then cuts deeply in the wild troughs.
In the past, many mills were set up along its tributaries and the river itself was used to transport timber to Tolmin. The border mark engraved into a rock is evidence to the past importance of the Tolmin forests and the rich history of forest planning. It is a sign used by foresters to mark the reserved royal forests (later, state forests), which used to provide timber needed by the state for the reconstruction of infrastructure, shipbuilding and trade with Venice. Royal forests in the Tolmin area included the forests of Kneža, Matajur, Kolovrat, Krn, Slapišče, Zadlaz, Tolminka, Kacenpoh, Bača, Podbrdo, Petrovo Brdo, Porezen, Klobučarji, Kopovišče, Hotenja, Dolenja Trebuša and Veliki Prošek, Izgora and Strmarica in the Bovec area. The forests were first measured in 1736. At that time all royal forests in the North Primorsko region were mapped and the maps included forest border marks and the year of measurement. The first forest management plan ever to be made in Slovenia was prepared for the Tolmin forests in 1770. The plan, based on sustainable forest production principles, was drawn up by Franz Flameck. In 1803 a new forest delineation map of the Tolminka valley was designed. At that time, border marks were reinstated and the year 1803 sign was added, whereas the letter W is a former mark of a state forest (Waldung).
The author of the map was Natalis Schneider, a forester who had previously designed klavže, huge water barriers built to help bring timber downstream. They were set up on the Tolminka river below the Polog pasture by the Italian company Santo Businelli after it signed a lease contract for the exploitation of Tolmin forest in 1768.