This incredibly huge lens is the Perkin Elmer 36-inch f/4.0 Aerial Camera Lens, and is up for sale on eBay for a mere $5,000 — though shipping it wont' be cheap. At 35-inches long and with a 12-inch diameter lens, it's a 200 lbs monstrosity, designed for use by governmental aerial photography. According to the listing, this lens was used by the U-2 SR-71 Blackbird spy plane, and others of this type were used in the Samos satellite system.