I lived in Rome for a time, as a research assistant at the British School. One of the perks of the job was getting invited along to urban sites recently discovered, or newly re-opened (especially the levels beneath the churches!). In that vein, courtesy of Pmog, I’ve come across the following sites that are worth a visit:

http://www.arssubterranea.org/

We like to play inside ruins.

Ars Subterranea is comprised of artists, historians, and urban explorers working to create an intersection between art and architectural relics in the New York City area.

Our aim is to instigate unique perceptions of New York’s history by constructing narratives around the city’s forgotten relics. Ars Subterranea encourages its audiences to interact with the city’s neglected and ruinous locations by recreating obscure but fascinating aspects of its urban development. Our projects include art installations, history-based scavenger hunts, unusual preservation campaigns, and much more.

We invite you to find out more about our past and future projects and to contact us if you would like to know more.

I like what those folks are doing: archaeology as performance!

And from the other side of the pond,

http://www.subbrit.org.uk

Formed in 1974, Subterranea Britannica is a society devoted the the study and investigation of man-made and man-used underground places. Cold War related material is covered separately here: COLD WAR -Bunkers etc. Subterranea Britannica brings together people with an interest in all types of underground space – from deneholes to dug-outs and from souterrains to subways – see the sites pages. Indeed, as the list shows, there are at least seventy categories of underground excavations that are of particular interest to our members