The construction of the castle in Świecie began around 1335. It was located on the fork of the Vistula and Wda rivers. The Vistula initially passed directly under the southern walls of the castle, while the Wda was separated from it. The outer ward protected the wide moat from the west. The next moat surrounded the upper castle on three sides. The outer ward had a plan similar to that of a rectangle. To the west there was a gate with a tower and a cowshed, from the south – the house of the commander and stables, and from the north perhaps also the armoury and infirmary. Surrounded by the parcham, the convent house was built on a square plan with a cylindrical “bergfried” (tower) in the north-west corner and three lower cylindrical towers in the other. It had two fully raised wings – in the north it housed, amongst others, a chapel and refectory, and in the eastern wing a brewery, bakery and dormitory. From the south and west there were single storey buildings present in the Middle Ages, housing a kitchen (in the south) associated rooms and a basement (in the western wing). Based on the analysis of architecture and the results of archaeological research it is possible to reconstruct the stages and techniques of construction. After setting the proportions of the building by the “ad quadratum” method, a perimeter curtain wall was first built. Subsequently, the internal buildings were successively constructed from the main (northern) wing. The area of the courtyard and the parcham were raised by 2–3 metres. Subsequently, the upper floors of the “Bergfried”, the parcham wall, and, finally, the outer ward were erected.