Beware of Urban Explorers....
National Counterterrorism Center: Urban Exploration Offers Insight on Infrastructure Vulnerabilities
Urban Explorers (UE)—hobbyists who seek illicit access to transportation and industrial facilities in urban areas—frequently post photographs, video footage, and diagrams on line that could be used by terrorists to remotely identify and surveil potential targets. Advanced navigation and mapping technologies, including three dimensional modeling and geo-tagging, could aid terrorists in pinpointing locations in dense urban environments. Any suspicious UE activity should be reported to the nearest State and Major Area Fusion Center and to the local FBI Joint Terrorism Task Force.
http://publicintelligence.net/nctc-urban-exploration/
Urban Explorers is a network devoted to the beauty of abandonment and ruin. With their motto in mind – “Take nothing but photographs, leave nothing but footprints” – pictures and videos are found all throughout the site, captured by explorers worldwide who seek desolated buildings, ghost towns, and any other structures formerly inhabited by people. Users of this site can discover a very real forgotten world filled with ghosts of the past – a defining element of “post-apocalyptia”.
http://www.makeuseof.com/tag/3-sites-prepare-apocalypse/
3 Sites To Fully Prepare You For The Coming Apocalypse
Whatever your flavor of apocalypse may be, it’s always a good idea to remind yourself that it might happen, so you really should ask yourself, “What am I going to do?” Naturally, in the case that humanity brings upon its own destruction, it’s quite likely that the Internet won’t exist, but that doesn’t mean it can’t prepare you while it’s still here!
Get ready to grab your rad-suit, crank up the chain-saw, or check the batteries of your Geiger counter. MakeUseOf is venturing out into the wastelands with these three sites.
Go there now (scroll down to third section for Urban Explorers)
http://www.urbanexplorers.net/
= new reply since forum marked as read
Unless terrorists become members of urbex sites, there is no way to, usually, glean info from the posts or photos posted. Urbexer's generally closely guard the locations of their finds because they don't want taggers, scrappers or authorities to know the location.
about 20th/21st-century infrastructure from pictures of an abandoned 19th-century farmhouse or grain mill or factory! 
How do these poor people ever leave their houses without dragging along a fainting couch?
