Okay, less blur, more detail. I switched the regular columns for a caryatid and a telamon, and filled the pediment with figures of the underworld. Not much detail yet but from left to right, the three judges of the dead, Persephone, Hades, Hekate, and the three furies.
I feel a bit silly for trying to do architecture and then immediately turning it into human figures, but I think the end result will be good.
@ Nickodemus - Thanks for the encouragement! I had a similar idea for making Cerberus part of the gates, but couldn't get it to look right. Too many heads got awkward for me. Waterwheels are a brilliant solution.
@ Rhazza - Sweet idea. I liked the previous perspective better though, it felt more dynamic, like the whole world is getting sucked into hades.