The term PERISCOPE SITE can be broken down into two words, SUB (3 letters) and SUBMARINE (9 letters). A periscope is an instrument used for viewing objects that are otherwise out of sight, usually by means of a tube with mirrors at each end. Submarines use periscopes to observe the surface of the water while remaining submerged. Therefore, a periscope site is a location where a SUBMARINE can be seen using a periscope.