What the dear NSA allegedly mean by "Mystic site"?

From cryptome: http://cryptome.org/2013/11/snowden-tally.htm

19 May 2014 12 Various Pages 12 http://cryptome.org/2014/05/nsa-intercept-14-0519.pdf p. 2 of the pdf: "Approx 10-15 SIGINT reports pers week from "Mystic sites" other than Sca....." 1. What does "Mystic site" mean to the dear NSA? 2. Is "site" in the usual computer sense?