The 1906 is a fairly easy trail. For more of a challenge and for the better in shape, go straight up Powerline and take Prairie Trail or go higher and come down the 1906 back to the trailhead/parking lot. Need ice trekkers in Feb as the snow turns to ice. The varying terrain keeps it interesting.
Gets lot of use even in winter on a good day. Has an awesome cave as you're going up. Need to be in relatively good shape if you plan on getting to the top. Incredible view of Helena and surrounding areas. Should be a requirement if you're just visiting/new to Helena.
Grizzly Gulch Drive is a porous road that continues after Helena's Park/Main Streets end. There are plenty of residential drivers, dogs and the potential for grizzly bears (yes, seriously, very seriously, the road's name is not cutely named, it's realistic, grizzlies are known to attack sheep outside Helena and there are many signs posted in this area warning of the bear threat). So it's not a great place for trail running, as I found out the hard way, but Grizzly Gulch seems like a nice access road for mountain biking. Take bear spray.