Ciechanów

Ciechanów grew around the castle of the dukes of Mazovia on the Łydynia. Built in the fourteenth century on an island at a bend in the river, the brick fortress replaced an earlier wooden stronghold and became a seat of ducal authority. Its towers and walls were raised during later alterations, giving it a commanding presence above the low, marshy ground beside the winding Łydynia river.

After the last Masovian dukes died without heirs, Ciechanów passed with Mazovia to the Polish Crown in 1526. Royal officials administered the castle, whose earlier political importance diminished. Swedish invasions in 1657 and 1708 damaged the town and fortress, and the castle fell increasingly into ruin. Ciechanów nevertheless remained a centre for the surrounding northern Masovian lands.