I think that the actual "vertical" section of Oblivion is 60 ft. It's a very clever illusion making you think it's vertical for much more than it is.
However, I do struggle to believe that it's actually 180 ft in total. That's a hell of a long way down and to pull out of in such a short space. However, it must be.
Here's the drop off Griffon's 200 ft lift hill:
Also, if you look at G5 (Oblivion's mirrored clone), you get some idea of the true scale of the ride. G5 looks much, much, much bigger than Oblivion:
Oh, and for pics of the area of Nemesis before it was built, look at photos of Thunders Looper and The New Beast - search for those and you'll come across some which also have the Nemesis area.