l will be climbing the CN tower in Toronto in 4 weeks- the tallest free standing structure in the world!There is 1776 steps or 144 flights.l have been training on stadium steps, but l feel unprepared for this number of steps.Does anyone have experience with this?

l hate to sound trite, but.by climbing stairs. It sounds like you are doing the right stuff.

Maybe add some weight lifting for your legs (squats, hamstring curls, lunges).

The only difference is, u will be indoors, with not-so-fresh air Im guessing. & this can cause u to go weak & lose ur momentum. l too have trained on stadium stairs & then tried to run stairs in a building, & the area is cramped, its different breathing.
Ideally, u should try to be as stretched out as possible, & wear thin shoes. Least weight as possible, it will make the difference. Im not kidding, wear as little clothing as humanly possible. Sports bra. but not too tight. & lightweight running shorts, & get some new shoes.

Some shoes have spring bounce action in the toes. l know of some Adidas (thats all l wear, so sorry l cannot give more brands as ideas), & they have some heel air pockets & some have toe bounce. Find some with the toe spring action.. this helps.

You should be training doing other things too, not just up & down stairs. But doing squats & lunges.
Focusing too much on one area will cause u to increase the risk of injury. Your overall body must be in good condition, because all it takes is for u to get tired & try to compensate by using another muscle group, & tear something because that other muscle group is poorly conditioned.

Try counting steps & music while u r training. Basically, u need to bring ur body to EXHAUSTION every training day, because u will be exhausted when u climb the stairs at the CN, & u need to be prepared to breathe correctly & to keep ur body moving, never stopping.

aegaergaergeg

Climbing steps (as you are doing), jogging up hill, try also using weights ~10lb when climbing steps or running. Once you do it without weights, it will feel easy.

Try the above, l just wanted to add that l am pretty sure the CN Tower is no longer the tallest building, which sucks, someone in Japan built a larger one or something.