One of the best places in London to get outdoors and to get some fresh air is Hyde Park.
Hyde Park is a Grade I-listed major park in Central London. It is the largest of four Royal Parks that form a chain from the entrance of Kensington Palace through Kensington Gardens and Hyde Park, via Hyde Park Corner and Green Park past the main entrance to Buckingham Palace. Wikipedia
Hyde Park Is where Londoners go to relax.
The Royal Park was once owned by the monks of Westminster Abbey but it was seized by Henry VIII after England's break with the Roman Catholic Church. The park has been the site of great exhibitions and demonstrations and is famous for the Speaker's Corner and the Marble Arch. The park is open to the public from 5am to midnight. The park has several restaurants wich are really worth a visit.
There is no charge to visit Hyde Park. So, what are you waiting for?