Drivers were slapped with fines as they ignored double yellow lines to park up at Dovestones Reservoir on Saturday.
The area was 'rammed' with people flocking to the Oldham beauty spot, according to posts on social media.
Photos showed a traffic officer issuing fines on a number of cars parked on the side of the road.
One social media user said: "Dovestone was rammed and so was the A635 leading up the moor.
"Lots of large groups walking the area."
Another described how the place was 'swamped'.
Twitter account Keep Dovestone Litter Free posted a warning, saying: "If you are thinking of coming to Dovestone be aware the car park is filling rapidly and cars and people are sliding all over the place."
Commenting on the post, another social media user said: "Wtf is wrong with people?!"
Under current government guidance, people are only allowed to leave their homes for a limited number of reasons.
People can go out to exercise, which can be with up to one other person from outside their household or bubble.
The exercise should ideally be limited to once per day, and guidance is that people should try to do this locally.
