It's a good one to visit but also consider the Sky Garden at 20 Fenchurch Street. Also known as the 'Walkie Talkie' building and famous for melting a car in the street! I would say the views here are better and you can visit for free if you book in advance. As part of it's planning consent there is a covenant allowing free visits. https://tickets.skygarden.london/WebStore/shop/viewitems.aspx?cg=SkyGarden&c=Tickets. You get a generous slot to take in the views, admire the plants and have bite to eat or drink. From memory the lifts are extremely fast too!
