ok best spot ever, and if tried quite a few.
RCoD in zun's room set your auto circle to 75 near the stairs faceing the left wall. you might want to hit invurn song first so you don't get wacked to much. its slightly dangerous at first but once you get a knack for it you can go for 24 hours+ without a death. and its worth it the xp is 7-12% aa exp at lvl 70. enjoy
p.s. don't stray to far from you pc though, this spot could get you banned if your afk to long.