The original plan was to take tunnel creek trail to 5050 pass and then to Valhalla peak, but we walked right past the tunnel creek trailhead and by the time we realized it we decided to just keep going
We didn't know about Lake Constance, but at this point we had walked on mostly flat ground for 5 miles and were up for something new
The trail climbs steeply (1,700ft of elevation gain per mile) and it's a bit of a mess with downed trees and other obstacles
About 2/3 of the way up the trail it becomes more mellow at times and the forest is beautiful. I think this is in the National Park but if it isn't then this would make for great camping.
We didn't actually make it to the Lake, it was a long walk back to the car and the sun was going down
On the way back we found the trailhead that we missed, this was about 30 minutes from the car which was on Dosewallips road (NF-2610)