Rowntree Park is ok, close to the city and yes a few bridges not far from you, a little quieter if you wander down the bank past Millenium Bridge (away from the city centre).
Knavesmire (racecourse) is a big spot and nice and open too and if you go high enough up you can get some good views of the city. If you fancy a ride out a bit further, take a look at Naburn Lock (park just beyond the caravan park) its where the river cruises turn round, and I’ve never been bothered down there, the lock keeper/caretaker chap is very amenable if you bump into him.
Heres a Hangar 360 I took a couple of years ago, from the middle of the city centre, straight up straight down, from one of works properties so no hassles.
Like any city depends on how many folks are about, if you want anymore info, please ask or PM me,