The image from Watford Borough Council shows litter strewn across the popular Watford park.
Empty glass bottles, cans and empty alcohol boxes were left after people gathered in the sun yesterday.
Dozens of plastic carrier bags and piles of burnt out rubbish were also left behind at the park.
Watford Council shared this picture of rubbish left in Cassiobury Park
Veolia workers were pictured cleaning up the mess this morning.
It comes after lockdown rules eased in England on Monday, allowing people to meet up outdoors or in gardens in groups of six.
Under the new restrictions, social distancing measures should remain in place.