This park is about 40 minutes west of downtown Denver, and while I did not see any bears or mountain lions (whew!), I did see lots of great birds. They have a nice parking area and the trails are open for use by horses, mountain bikers, hikers, and dogs, though a couple of short trails are restricted to hikers only. This was a pretty busy park with plenty of bikers and hikers and all of the dogs were well behaved with one exception (there's always one...). There were also plenty of fishermen and anglers enjoying the river. Facilities included bathrooms, picnic areas, and an educational area. The trails were easy to walk and level. Taking the trail upstream of the parking area, there were two stream crossings where you had to skittle across slippery rocks for a couple of feet, but these were a good ways down the trail. There are two bridges that can be used to cross the river, but at the time of my visit, the one upstream of the parking area (Dipper Bridge) was closed.
More info about Lair O' the Bear can be found here:
https://jeffco.us/open-space/parks/lair-o-bear-park/
as well as info about other Jefferson County parks.
Map of Lair O' the Bear: