Trams and  Tram trains of RBK in the diveunder section that allows access to the city streets
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/155511945@N04">Kevin Prince</a>
CC BY-SA 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/155511945@N04/49443012931/">Kassel Hbf</a>