I found this before 2-3 weeks.Now u know alliance base where are the arcs on second floor for doors.Now i had this 2 times.First time i was FC and was hiding there then a warlock feared me and i went through the corriodor and into the wall run the whole wall and get outside.Then the whole wall behind me was invisibile for me.Went there and fell down to the bottom of tunel and again i was behind the wall.I could see everybody but they couln't see me...
Here are some pictures...

[b]Please discuss.