Vivec, Arena, Waistworks. There are Canal works at two ends, one of these has doors leading to a Fighter's storage area. The storage area has rats, two doors on the left side, and one on the right (from where you come in). I believe the doors are locked, maybe max of 30? Go through the door on the right, and there's a level 50 hatch on the floor. This leads to the Morag Tong headquarters.
I think there was some decent stuff hidden in these storage rooms as well, if you want to look through all of it.