At just shy of 1300 ranks, I have had a lot of success with doing circuits of the undergondola, and all of the climables in the wyvern area. That takes over a minute, so you can just loop it a couple of times to lock. I hit every single climbable, because it's a tiny bit of exp but 0 RT, so it's worth doing.
I know someone else who used the same circuit, but added in the Shard walls, and took it all the way to cap.
