Spain
- In Barcelona, there's an abandoned underground mall near Plaça de Catalunya called Avinguda de la Llum, closed since 1990, which had originally been part of a more ambitious project to build an underground city under the centre of Barcelona. Also, some Metro stations or connecting lines in the same station are connected by underground passages over a block in length.
- Legend has that the many caves and tunnels under the old part of Toledo were connected and were used by occultists.
Read more about this topic: Underground City