To all out there who want to have a stunning view over London and to have an experience they will not forget so soon, book a time slot to visit Sky Gardens, located on the 35th floor at 20 Fenchurch Street. This 38-storey building is the fifth tallest completed building in the City of London and offers incredible 360 view.
The visit is free, however, you will need to book in advanced as every visitor is offered a time-slot. You will also have to undergo an airport-similar security check at the entrance.
Opening times are Monday to Friday 10am to 6 pm (last booking slot 4.30 pm) and on weekends 11am until 9pm (last booking slot 7.30pm). I had my visit on a Friday at 10am, it was really nice because it was not crowded so I was able to enjoy the view and take as many pictures as I liked without being interrupted. My mother and I sat down at the end of our tour at the cafe located in the garden-area, and enjoyed cappuccinos over the rooftops of London. From above, the city looked much more tranquil and it was a nice break away from the city's swarm.
As we entered the lift to get back to ground floor, the sir who was in charge of us arriving down safely was asked by another visitor which would be the best time to visit, from his point of view. He mentioned after sundown, when all the city is lit and you can have another experience than during the day. I saved myself that experience for my next visit to London. However, if you visit London for the first time and you are not very familiar with its geography, I recommend the day-time visit.
Have fun and enjoy!