So, as they guide you through, is it rather fast paced? I can handle stairs if it's not rushed. I'd really like to see this place.

No their don't rush you and going back you can go at your own pace.I did ok going down but had trouble going back up the stairs. The guide stayed with the last ones out to make sure everyone in their group was accounted for

If you can walk up a18 story building you will do fine.

Each step down I got anxious about my asthma. On the return, I just paced myself. No matter where you are in the path, you are half way back. I was fine. Just took my time.