this is probly very very old and im not even sure if its been posted before but heres a way to get ontop of IF AH it can take some time but is cool
Now get outfront of AH and jump onto the right side rail thing.
move along it and jump up onto the wall rim thing (ignore my descriptions i can't think of anything else to call em)
ok now that you have jumped up their go between the wall and AH
ok run into the corner and start jumping and pressing foward into the corner to wall climb up when u get near the steel rim above ur head and ur above the AH roof but still next to it drink a swiftness potion or use sprint and jump across this can be very hard sometimes
k done don't have a screenie of me up their cause i got up their, while editing i accedently deleted it and it took me good 10 minutes to get up their, im too tired to do it again their yous go and night