Chełmno, Tower of <a href="https://en.wikipedia.org/wiki/Mestwin_II_of_Pomerania" class="extiw" title="en:Mestwin II of Pomerania">Mestwin</a> (probable Teutonic Knights' watchtower) and western gable of Cistercian nunnery
<a href="//commons.wikimedia.org/wiki/User:Pko" title="User:Pko">Pko</a>
CC BY 2.5
<span class="int-own-work" lang="en">Own work</span>