The article highlights the site on the hillock called Võnnumägi less than 1 km from the fort of Keava, which was discovered and excavated within the Keava project. In view of the fact that one end of the hill was cut off with a prominent rampart, the site can be classified as promontory fort; other sides of the enclosed area were without fortifications. Unlike in typical hill forts, there was no definite occupation layer in the compound. A few potsherds and radiocarbon dates prove that the site belongs to the Early Pre-Roman Iron Age. Among the known hill sites of the time, Võnnumägi is standing out as the only one having a substantial earthwork barrier, whereas the rest of the sites have had some wooden defences or had no artificial fortifications. The function of the site is still disputable.