The Clink Restaurant at HMP Cardiff has been voted the city's best restaurant on online review site TripAdvisor.
The 96-seat restaurant, which is within prison grounds but outside the main walls, came top out of 946 other venues and was complimented on its "friendly and informative staff" and attentiveness to guests' needs, the Telegraph reports.
Other users called the site "an ace idea" that "offers people a chance to start again", while the food has also been hailed as "excellent", with a "small menu but a really good variety of choices".
The second and third-rated Cardiff restaurants are the Italian sites Il Pastificio, and Café Citta, respectively.
The Clink Cymru is staffed by Category-D prisoners, who are also trained in official hospitality qualifications, which aim to reduce recidivism rates by providing inmates with useful skills that they can draw on once released.
The Cardiff site is the second for the Clink Charity, which set up its first restaurant inside HMP High Down in Surrey in 2009 under catering manager and Education and Training 2011 Catey winner Alberto Crisci. In both site, prisoners are paid a nominal wage for a 40-hour week.
General manager Jason Lawrence told the newspaper that the Cardiff team was very happy to have been ranked so highly and thanked customers.
He said: "The recognition we have received from so many of our diners for the atmosphere we've created, the effort we put into sourcing our ingredients, the high standard of front of house service offered by the waiters and the skill our menus is incredible."
The original Clink site has attracted much support in recent years, with chefs such as Giorgio Locatelli, Antonio Carluccio and catering consultant Vic Laws becoming ambassadors and "chef lecturers" at the 85-cover restaurant in 2011.