A Geek's Guide to the World!
I've just updated the Geek's Map* with this entry along with the recent Osowka one (https://forums.theregister.co.uk/forum/2/2018/01/11/osowka_underground_city/), which was filed under bootnotes.
I posted a quick comment on that article, but as it is already a bit old and might not be noticed, I thought I'd re-post here: is the Geek's Guide going to expand to Europe? Heck, why not get the American and Australian Vultures involved too?
A Geeks Guide to the World! It would make for some fun diversions whilst on holiday.
*http://www.gypsythief.org.uk/GeeksMapToBritain/ is a map of all the Geek's Guide to Britain sites for those who don't know. (But please try not to boot me off Mapbox again for exceeding my free views! (although they let you straight back on again, so whatevs :))