On my first tour around London, one spot the tour guide made sure to point out is 20 Fenchurch Street, more commonly known as The Walkie-Talkie, and it's infamous Skygarden. It's infamous because part of the reason the Walkie Talkie was allowed to be built was the company’s promise to create a public garden in London. What they didn't tell anyone was their plan to built it at the top of their skyscraper.
To get your free enterence to the SkyGardem you have to book online on their website I would advise booking the first day of the month when they release the tickets for that month because they get booked up quickly. Online, you simply choose the day and time you want and book with your name and email. It is perfectly free. Then, you get sent and email with your ticket that you can save on your phone. Just make sure to bring an ID that matches the name you gave on the ticket. They really do check IDs.
To get to the Skygarden, I took the tube to Monument station and honestly just kind of wandered around until I saw the building. It's very tall and obvious as long as you look down the right street. You can also always just look up an online map, but it is very close to Monument and Bank station. Then, do not go in the front door. This is for general business. If you go around the right side (or ask one of the security guards) you will see a little area with benches and a café and a door labeled SkyGarden. You really should get their about 10 minutes early; do not get their late because your ticket is only good for your time and the next time is 15 minutes after the first. Once their, they check your ticket and ID and you go through security, a airport style scanner for bags and coats and a metal detector. Then, you take a very fast elevator up to the 36th floor.
I really would not go to the Skygarden if all you want is a garden experience. The garden is pretty but really just a few large planters with some plants. The real reason to come is the view. You can walk around the perimeter of the building and so get a 360 degree view of London. They also have a viewing platform that is open air that has a great view of the Shard. What is also great is that this is all free and many of the other high views in London like the Monument and other skyscrapers you have to pay to go up.
They also have a few cafes in the Skygarden and tables and couches that you can lounge around the garden for a while. The prices also are not that bad; you can get a party and a coffee for around Five pounds. Also, as an FYI there is apparently an one hour time limit, but I do not know how they enforce it. Really, if you do not eat, you only need around a half hour.
Overall, it was an enjoyable way to spend my morning. It was free, easy to find, and provided a great view of London. I would like to come again around sunset next time, I'm sure the view would be great.