UPDATE!!! Undersea Adventures is back to offering scuba diving tours of the flooded missile silo near Royal City, Washington!!!  This is the best day ever! Check their website for prices and a schedule.  Be sure to check out the artist's rendition of the entire complex: under the form on http://www.underseaadventures.net/silo.htm.   2/8/2010 A few years ago I heard that a friend of a friend had gone scuba diving in a missile silo in central Washington.  It sounded like something that I should be doing too.  It took some digging but I finally found out where they must have gone: Site 568-C near Royal City, Washington.  This is an underground silo that formerly held one of the gigantic Titan 1 missiles.  What an awesome place to go diving! I contacted a dive shop in Tri Cities (Undersea Adventures) that used to lead trips there.  The silo is on (or under) a farmer's property.  It sounds like there is some kind of issue with some contaminated dirt that is somewhere near the silo.  I was under the impression that the "contamination" is from small fuel spills that you would expect on a farm.  It didn't sound like a big deal (to a non-government official), but it is enough to temporarily put a stop to the diving.  Which doesn't seem fair because I really want to go there.  Maybe somebody out there knows how to deal with dirty dirt and can help solve this problem... I found a great article about diving the silo (linked below).  You should check it out - it sounds very very cool!  It sounds like there is a network of tunnels and support silos but most people are only allowed into the main silo.