The Sky Garden is located at the top (37 storeys) of the new Walkie Talkie building at 20 Fenchurch Street.
You can either make a reservation in one of the restaurants (Fenchurch Restaurant / Darwin Brasserie) or one of the bars (City Garden Bar or Sky Pod Bar). Alternatively you can book a free visit through the website to walk around the gardens and take in the views of London!
I visited in the morning and had a hot chocolate and a muffin at a table overlooking the city. A cost effective way to have breakfast and beautiful views of London.