Merthyr Tydfil has become the first area in Wales to begin mass coronavirus testing for people who do not have symptoms.
Everyone living or working there can now get a free test.
It follows a similar scheme in Liverpool, and members of the Armed Forces are again involved alongside local authorities.
The aim is to identify more positive cases and stop the disease spreading unchecked.
Merthyr Tydfil Rhydycar leisure centre opened for testing on Saturday and other sites will come online later this month.
Lateral flow tests are being used - they give a result in around 20-30 minutes and do not need sending to a lab.
People who test positive will also get a traditional swab test - which has a higher degree of accuracy - and will be asked to return home to self-isolate.
Health Secretary Matt Hancock has offered the rapid tests to every local authority in England, as well as the devolved nations.
Merthyr Tydfil saw a significant drop in cases following Wales's recent "firebreak" lockdown, from around 770 cases per 100,000 people to below 260.
Blaenau Gwent in South Wales is now the country's virus hotspot, with more than 350 cases per 100,000.
Overall case numbers in the country dropped over the 10 days leading up to Friday, and there are also signs of a slowdown in hospital admissions.
The country's seven-day incidence rate is now around 160 cases per 100,000 people, according to First Minister Mark Drakeford.
Despite the success, he said there was "no room" for further relaxation of the rules.
"We need everyone, every single one of us, to play our part to make sure that we continue to build on the progress of the firebreak, and to keep coronavirus cases falling," Mr Drakeford said on Friday.
He added: "If we do all this together, then we can have a path through to Christmas and will be hoping to see family and friends over that festive period."
Mr Drakeford has said talks on a UK-wide approach to Christmas rules are planned for next week.
