In the interests of science (and this forum) I visited Horizon22, the viewing platform at the top of 22 Bishopsgate, a new-ish tall building in The City of London.
I was passing on my way to catch a train and the display outside alerted me to the fact that walk-up tickets were available. Booking a ticket required scanning a QR code by the entrance and filling in a short form. There was a brief security check in the entrance lobby and plenty of friendly staff to guide one to the elevator. The elevator ride made my ears pop.
On arriving at the top, there's more staff to greet you and the lift brings you out on a mezzanine level of the viewing floor. There's floor to ceiling windows and a fairly bare large room to walk around and take in the view.
There's a great views west east and south, with no view north as such. Even on a dull, rainy afternoon in December the views were good. There's many landmarks to see, with particularly good views of Tower Bridge, The Tower of London and HMS Belfast. All the signature tall buildings in The City can be seen and Canary Wharf was looming out of the rain to the east. I could see The Houses of Parliament to the west and a staff member pointed out Buckingham Palace. I could see the transmitter tower at Crystal Palace, which is seven miles away, so visibility wasn't too bad considering the poor weather. The chap I spoke to was very friendly and pointed out a few landmarks, including Finsbury Gardens and Finsbury Square, which I didn't recognise from up high.
It wasn't too busy. Plenty of room at the windows to walk around and linger looking at stuff. No seating and only a small coffee counter and bathrooms as facilities. Some youngsters were sitting on the floor and it didn't seem to bother anyone. It was a grey day today, so the availability of walk-up tickets might be less on a better day. Definitely worth a visit, especially if you're seeing other things in The City.