The construction of brick fortifications in Lidzbark Warmiński (Heilsberg) began after the town was established under Chełmno law in 1308. The date of completion of the works is 1357. During the construction, the location of the city on a slightly hill and natural boundaries were used, such as the Łyna river flowing in a large bend in the south and east. Most of the fortifications were pulled down in the 19th century.
The circumference of the defensive walls was irregular, adapted to the slight rise and bend of the river. The total length of the walls was about 1000 meters. Their height originally amounted to 5 meters, and after the extension in the fifteenth century it reached 7 meters. The north and west sides of the circuit were reinforced with half towers, open from the town side. Lidzbark owned three town gates: Mill Gate connecting the northern outer bailey of the castle with the town, High Gate with foregate from the north-west and Church Gate from the south-west. In addition, there was also a wicket gate called Castle Gate. External fortifications were moat of the castle from the east, and from the south the river Łyna.
To this day, a part of the curtain of the northern fortifications with a half tower and the impressive foregate of the High Gate in the north-west part of the old town have survived.