I have two flights of stairs in my home, and find that on days that I can't get to the gym or get outside, climbing those for 45 minutes with a 50lb pack is MUCH better than nothing. During my training phases, I climb stairs 4 times per week, bike 3 times a week for 20 miles each trip making sure to incorporate steep inclines, weight lift, and eat healthy. I also do outdoor hill climbs with a full pack, and find that the 100ft hill behind my house, which is also a 45 degree incline, is a great training hill.....especially in the winter when they're covered with snow from Nov through April. I'll also use those hills for interval training where I'll walk up and down for 15 minutes, and then do 5 minutes of sprints. I also get into the mountains a few times a month and get into the Black Hills when the mountain passes get tricky(I'm 50 minutes from the Bighorns and 45 minutes from Devils Tower). There is no substitute mountaineering like mountaineering......but that escalator idea is brilliant.