There are actually 2 sections of wall to climb at Doan Brook. The first is rather unimpressive and is about 20 ft high with only a few routes to the top and a few places to boulder. This is located where Delaware St. would be if it continued across North Park into the ravine.
The other section is much better and is about 30ft high with many more places to climb. It is located where Roxboro St. would be if it also crossed over North Park into Doan Brook. I'd say the wall is around 30ft high and 100ft wide. This has some nice jagged rock with a lot of great holds and lots of opportunities for routes and bouldering. There are also a few sturdy trees leaning over the top that have the possibility of setting up a top rope. The only issue is that in the summer it is constantly moist and thus slippery and has mosquitos and spider webs.