I did a gravel race last year that was 9300' in about 80 miles, almost entirely off-pavement.
Done lots of other gravel races that have >100' per mile of climbing.
Also done some of the classic Colorado climbing events, like the
Mt Evans Hill Climb. They don't necessarily have sooo much climbing, but it is concentrated in fewer miles. I think the Mt Evans race is about 28 miles long, with about 6700' of clmbing -- so, that's about 240' per mile, if I'm doing the math correctly.
Also done the
Pittsburgh Dirty Dozen, which is a big climbing event in a city that, unbeknownst to many people, is actually extremely hilly.