Green Park is a charming park next to Buckingham Palace and is one of the royal parks.
Green Park isn't typically a destination in and of itself, but the journey to Buckingham Palace will typically lead you through the park. On sunny days you may, however, find many people enjoying the outdoors and having picnics.
You can also rent deck chairs between March and October if the weather allows it. The chairs are £1.80 for the first hour and £9 for the whole day.
Green Park has its own underground station, which can be accessed via the Jubilee, Piccadilly and Victoria lines.