And nowadays, a Trek 520 is STILL the most touring friendly bike in Trek's lineup.
I just laid down 220 miles on one as an overnight, including 80+ miles on gravel trails and roads.....the Trek 520, when sized right, and fitted with fattie tires, will ride ANYTHING you are capable of piloting the thing down...and that includes technical single track. I ride single track on mine fairly frequently.
for those of us not willing, able, or skilled enough to retrofit an old mountain bike, a Trek 520 will take the rider anywhere they want to go, and do it faster and more comfortably than a mountain bike.
Think.....CUNNINGHAM RACER.......