Those who gathered have now been condemned by officials for breaching coronavirus regulations.
Covid-19 rules in Wales only allow six people from two different households to meet outdoors.
A Cardiff Council spokesman said: “Once again our teams have been faced with the huge task of cleaning up a significant amount of rubbish left behind by large groups of people intent on breaking Covid-19 restrictions.
“Last night, bins were left unused and the ground was littered with rubbish. Council staff have been on site since the early hours of the morning, working hard to clear and clean the area.
“Despite the preventative measures put in place by the council, in partnership with South Wales Police, the Welsh Government’s coronavirus regulations were again broken by a significant number of people illegally gathering in Cardiff Bay.”
Unsurprisingly, people were not impressed.
I wanna be out with my friends as much as anyone but Cardiff bay will be the reason we’re staying in lockdown 😭😭😭😭 sad
It follows similar scenes outside the Senedd in Cardiff earlier in the week, when three police officers suffered minor injuries when bottles were thrown.
First Minister Mark Drakeford said at the time that he was “shocked” by the amounts of litter and rubbish.
“I’ve seen the photographs and I’ve seen the accounts on television, and to be honest that is shocking,” he told BBC Radio Wales. “I’ve been a strong supporter of the police’s approach in Wales of inform, educate and persuade, and that is absolutely the right thing to do first.
“Where people deliberately and intentionally set out to do things that can cause a risk to other people, then both local authority and police have powers that they can use.”
Mr Drakeford said he was concerned the progress Wales was making in controlling the spread of coronavirus could be undone by people ignoring the rules.
Cardiff isn’t the only place that’s witnessed ugly scenes like this in the past few days. Last week, the lifting of coronavirus restrictions in England coincided with a miniature heatwave that saw thousands of people descend upon their local parks and beaches to embrace the warm weather and a small step back towards normality.
The following day, social media was flooded with pictures of parks, beaches and other public areas that resembled something closer to a rubbish dump than a natural location.
This, for example, was Hyde Park in Leeds on Wednesday morning:
#HydePark in #Leeds this morning after people came to the park yesterday during the hot weather. https://t.co/YtxuQ4vOdg
Fantastic to see so many ppl enjoying the sunshine in Sefton Park today🌞
To make the day better for every1, pls pu… https://t.co/7ax82c3rJk
— The Friends of Sefton Park (@The Friends of Sefton Park)
These scenes are reminiscent of what happened last summer when beaches from Brighton to Sunderland were left resembling waste sites as tonnes of rubbish was left behind by those visiting the coast for the day.
Prime Minister Boris Johnson has urged everyone in the UK to remain cautious and safe, especially over the Easter weekend.
Let’s hope those choosing to ignore this advice are in the minority.