The first Kaunas castle was one of the four castellum-type castles built on the territory of the Grand Duchy of Lithuania in the middle of the XIVth century. It was situated on the left coast of the Neris, approximately 6,00 metres to the north-east from the confluence of the Nemunas and the Neris, in a neglected archaic settlement (pic.l). According to the findings, the settlement dates back to the Xth - XIIth century (pic. 2). By the end of the XIXth century the Neris had washed away the main part of the castle (pic. 3). The defensive complex of the castle, the size of about 4 hectares, consisted of a trapezium stone castle with the walls of 12 metres high and 2.5 metres thick, the defensive ditches in the eastern and southern parts, defensive fortifications at the bottom of the defensive ditch and two brick towers (pics. 3, 11-13). The walls of the castle were made of stone (pics. 4-5), whereas the shooting gallery, gates and most probably the top of the walls and the decoration band on the external walls were made of brick. The area of the castle yard was 5200 m2. The investigation shows that the construction of all planned fortifications had not been finished until the attack on the castle in 1362 (pic. 10). It is estimated that for the building of the castle about 16,000 m3 of building materials was utilised. From the defensive ditch about 70,000 m3 of gravel must have been dug out. In the yard of the castle there were wooden houses and outbuildings (pic. 6). During the period of research very few artifacts were found, and these include pots decorated with stamped ornaments (pics. 7, 8). The main body of findings consists of a crossbow, an arch and balista arrow-heads lost during the attack in 1362 (pic. 9). The real possibilities and conditions for building the first Kaunas castle were already existant at the end of Gediminas' rule. However, the necessity of doing this in practice arose after the Strėva battle in 1348 due to the fact that the march of the Order of Crusaders was the first real menace to Vilnius, the capital of the Great Duchy of Lithuania. The spade work of building the first Kaunas castle started in 1359-1360, the construction was started in 1361 but it had not been finished until the spring of 1362.