Tunnels of the Downtown line
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/84044568@N02">SgTransport</a> from Singapore, Singapore
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/sgtransport/11689805973/">Downtown Line Tunnel</a>