For me, 3509m (about 11.500 ft) of climbing as part of a 301km ride with my wife, but it didn't feel like a lot of climbing because there was nothing particularly steep about the route, a couple of long gentle climbs and some (well, many) short hills at a moderate gradient.
I've had shorter rides which felt much harder, climbing wise; did a 2400m (7800 ft) as part of a 145km ride recently while on vacation where I also chased a few poorly contested climb segments segments on the way, and then ran out of water between towns (never rode there before, turns out there's a 40k stretch without a cafe or shop in sight, luckily it was something like a long -0,2% but running out of water still takes a bit out of you) and by the end of it, I was really quite glad it was over by the end of it.