Tunnel start on compound curve to corner 4 from left
<a href="//commons.wikimedia.org/wiki/User:Useddenim" title="User:Useddenim">Useddenim</a>
2023-04-23
Own work based on: <a href="//commons.wikimedia.org/wiki/File:BSicon_tkSTR3%2Bla.svg" title="File:BSicon tkSTR3+la.svg">BSicon tkSTR3+la.svg</a>