In reply to Ben_Climber:
I've seen a few people who've wanted to build the tallest wall in the country / Europe / world. They get all exisighted about how amazing it'll be until I tell them all the problems with having a 40m+ climbing wall.
Firstly, noone has long enough ropes, and putting in belay ledges and stuff if loads of hassle.
Then they realise it takes people ages to do one route so you can't have many climbers use it per hour.
Then they want it to be "extreme" but at the same time be inclusive and have routes for all abilities, until they realise only reasonably fit and capable climbers can get up a wall that tall.
Not to mention the expense for so few climbing lines, after a while they settle on somthing about 20m tall max like sensible people.