The Grūbele Hillfort is in the territory of the old Selonia and is considered one of the Selonians’ hillforts. It is 30-35 meters high, indivudual, round, flat surface, sandy, covered with pine forest. The northwest and southwest slopes are steep, and three terraces emerge on the other sides of the mountain. The hillfort has neither ditches nor ramparts, and its sloping site has been partially leveled due to excavation work. A small cultural layer is barely noticeable on the site, and on the eastern side, under the sand layer, a carbonaceous layer of earth was unearthed at a depth of two meters. At the foot of the hill and on the slopes, many trenches from the First World War can be seen, one of them encircles the hillfort from the top to the foot. The hillfort has been more archaeologically explored than it is mentioned in historical chronicles. In 1926, the measurements of the hillfort were made by Ernests Brastiņš and described in the notes of the exploration expedition of Semigallia hillforts. At the end of the 20th century, the hillfort was also explored by archaeologist Juris Urtāns, who in 1995 found a shard of molded striped pottery in it. This very roughly allows us to date the mound to the 1st millennium BC or the first half of the 1st millennium AD. A number of early and Middle Iron Age graves can be found in the surroundings of the hillfort. Many tales have been recorded about the Grūbele Hillfort, telling of the church that once stood on the hill and then sank. One of the tales says that the church on the hill had a bell and that the whole land rang with its ringing on Sunday mornings. The Devil in the underworld got angry at the disturbance and decided to sink the church, which the Devil did. The story goes that if you go up to the mountain in the morning and put your ear to the ground, you can hear the wonderful sound of the bells.