Köismäe tower in <a href="https://en.wikipedia.org/wiki/Walls_of_Tallinn" class="extiw" title="en:Walls of Tallinn">Tallinn City Wall</a>, Estonia.
<a rel="nofollow" class="external text" href="http://mstyslav-chernov.com/">Mstyslav Chernov</a>
CC BY-SA 3.0
<span class="int-own-work">Self-photographed</span>