UTL is about exploring past, present and future urban technologies in science and fiction, etc...
https://en.wikipedia.org/wiki/San_Francisco%E2%80%93Oakland_Bay_Bridge
https://www.sfchronicle.com/oursf/article/See-the-twin-Bay-Bridge-that-nearly-14416310.php
https://en.wikipedia.org/wiki/Yerba_Buena_Tunnel