I am the "colleague" matt speakin' about ! (member from today ! and sorry for my frenc.... english)
of course I think that area 51 is an "underground" facility and may be bigger than we (... I !) think !
if you have uploaded Google Earth, try some of these locations :
37°44'43.75"N - 116°27'12.28"O
or : 37°29'9.94"N - 116°13'31.08"O (to groups of circles on the same screen)
and this kind of geometric draw :
37°37'36.22"N - 116°57'29.63"O
ask me if you want more !! or post comments if you find others !
all these locations are about 150 km around Area 51 !
If somebody have any other explanations for this kind of "stranges circles" please tell me !!
(just for fun on Google Earth look at 37°38'47.64"N - 115°45'4.06"O , for a french boy it' quite "funny"!)