The tunnel is 2.3 miles of dark, cold and dripping. It was crazy crowded with hiker/walkers, bikers of all types. I rate it easy as long as you can walk 5 miles. Be careful, some little kids were not paying attention an nearly go hit in the dark. Some others had no light or it died. So have a back up. Light jacket in summer while in tunnel is a good idea. If you park at the Hyat lot at east tunnel entrance you need a discovery pass. There is day pass envelopes there and rest rooms. I am