The hillfort is located in the middle part of a promontory of the upper terrace of the Nemunas River. The platform is triangular, with its corners pointing northwest, southwest, and east. The western edge is 20 meters long, the southeastern edge is 18 meters long, and the northeastern edge is 22 meters long. Two meters below the platform, on the slopes, there is a 4-5 meter wide, 0.5 meter deep ditch, behind which a 6-7 meter wide, up to 1 meter high rampart is built. The rampart and ditch have survived only at the corners of the platform, while on the sides, 2-3 meters below the platform, they have turned into 2-6 meter wide terraces. The slopes are steep 8 meters below the terraces. On the southeastern slope, 10 meters below the terrace, there is a 7 meter wide terrace. On the northwestern slopes, 8-10 meters below the platform, there is a 4-6 meter wide terrace that resembles an old road (now a forest path runs along it). The slopes are steep, about 40 meters high. The eastern slope is the lowest, only 12 meters high, and further to the east, there is a 10 meter wide lower part of the hill, which connects with the highland at the edge of the valley. Therefore, here, 8 meters below the platform,
a second 5 meter wide, 0.3 meter deep ditch was dug, behind which a 0.2 meter high, 6 meter wide rampart was built. 20 meters east of the rampart, 2 meters above it, there is an oval, elongated west-east oriented, 17×9 meter flat platform. Its eastern slope, 3 meters high, descends into a hollow separating the hillfort from the highland. The hillfort is located in a spruce forest and is also known by the names Juodkočiai or Lapainia.
The hillfort is dated to the 1st millennium – early 2nd millennium.
The hillfort is called the French Mountain. It is said that French soldiers once came here and built the hillfort with their hats.
It can be reached from the Kruonis-Darsūniškis road (road No. 1803) by turning right (north) immediately after the Varkališkiai forest and driving to the current mouth of the Lapainė River. It is located in the forest, 200 meters east of its western edge, at the level of the mouth, going through a valley between two hills with a small stream (the left (north) part of the hill is now cut (slope) – it is on the right (south) hill). It is harder to find, as the upper terrace slope of the Nemunas River in this area is cut by similar deep ravines.