I was passing through Hidden Valley in FONV and looked at the graffiti. There I noticed a small bit of ink that reminded me of the years that I lived in the Basque country. There at the time and still now there was a movement of ETA that promoted basque separatism. and this was one of their main symbols.
http://www.shutterstock.com/pic-7565008/stock-vector-vector-map-of-basque-country.html
One of the graffiti symbols on the entrance looks almost exactly the same.
Does anyone else think so???