A bridge over Wisła River destroyed by Polish sappers in September 1939 in order to slow down German Army. 
Better photo:<a rel="nofollow" class="external free" href="https://img.audiovis.nac.gov.pl/PIC/PIC_2-7554.jpg">http://img.audiovis.nac.gov.pl/PIC/PIC_2-7554.jpg</a>
Unknown author<span style="display: none;">Unknown author</span>
<ul><li><cite class="book" style="font-style:normal">Apoloniusz Zawilski (1972)      <i> "Bitwy Polskiego Września" ("Battles of Polish September")</i>, <a href="https://en.wikipedia.org/wiki/en:Warsaw" class="extiw" title="w:en:Warsaw"><span title="capital and largest city of Poland">Warsaw</span></a>:  Nasza Księgarnia  <small><a href="//commons.wikimedia.org/wiki/Special:BookSources/83-218-0817-4" title="Special:BookSources/83-218-0817-4">ISBN 83-218-0817-4</a> (current edition)</small></cite></li>
<li><cite class="book" style="font-style:normal">Maria Turlejska (1966)      <i> Prawdy i fikcje: Wrzesień 1939 - Grudzień 1941</i>, <a href="https://en.wikipedia.org/wiki/en:Warsaw" class="extiw" title="w:en:Warsaw"><span title="capital and largest city of Poland">Warsaw</span></a>:  Książka i Wiedza, pp. s. 32  <small>no ISBN</small></cite></li></ul>