Brockwell Park
A large hilly green park; 10 min walk from the centre of Brixton. Has the following facilities: Brockwell Lido, children's play area, paddling pool, café, flower gardens, sports facilities, toilets and several ponds. Brockwell Park also has a BMX track.

A large hilly green park; 10 min walk from the centre of Brixton. Has the following facilities: Brockwell Lido, children's play area, paddling pool, café, flower gardens, sports facilities, toilets and several ponds. Brockwell Park also has a BMX track.
Check the official site before travelling; hours and prices can change.
More parks

Hampstead Heath
320 hectares of wild north London — swim the ponds in summer, climb Parliament Hill for the skyline.

Greenwich Park
Royal park with the Observatory at the top — best skyline view east of central.

Regent's Park
Queen Mary's rose garden in June. Primrose Hill at sunset, year-round.
Source: wikivoyage