Coliseum Mountain is a long and difficult trail with an amazing view as a reward. It is possibly the most difficult trail in North Vancouver.
Start this trail by following the Norvan Falls trail. You will turn right to go uphill right before the turn to Norvan Falls. There is a sign post telling you to turn. If you get to the Norvan Falls turnoff or the metal bridge, you've gone too far. The trail to Norvan Falls will be busy, but once you turn off onto the trail to Coliseum Mountain, you will see far less people (you might not even see a single other person). The trail immediately goes steep uphill for a while. The trail is marked, but in particular in the steep section, you need to pay attention to see the trail markers.
Once you finish the steep section, the trail goes slowly uphill the rest of the way, but mostly not very steep. This part of the trail gets quite muddy and there are several sections with the wooden lilly pads to avoid some mud. There will be a few short detours in order to get a view point. They are all worth taking.
Once you get close to the peak, there will be a couple really short scrambles. None are exposed, but you still have to be more careful while scrambling.
From the peak, you can continue on to Mt. Burwell, or just down to some small lakes to have a swim.