DRAB. Grey. Bleak. Functional. These are the kinds of adjectives associated with prisons, hospitals, homes and other ageing institutions built in a time when little thought was given to the experiences of the people they served.

True, prisons are not normally regarded as places where people should feel comfortable, but for those left on the outside, the prisoners' families, visiting loved ones can be a pretty depressing experience, quite aside from the trauma of physical separation.

And true to form, Saughton Prison sits grey, bleak and incongruous behind a row of houses in a neat Edinburgh suburb. Before March of this year, incomers reported for their pre-booked visits to uniformed officers inside the prison behind a wall of bullet-proof glass. Now, thanks to a team of bright young Glasgow architects and an enterprising charity trust that sponsors projects in British penal institutions, Saughton has a brand new visitor centre where people can book in at reception, leave belongings, have something to eat, entertain their children, obtain advice on everything from health to housing and find a secluded place to talk.

Architect Gareth Hoskins designed the centre with his associate Liam McCafferty. But this wasn't his first foray into a prison project. "I worked with the Outward Trust on a project on Bellmarsh Prison in London, creating a welcoming purpose-built environment for people coming into the compound," he explains. Hailed as a success, the Outward Trust and Saughton Prison held a competition for architects to come up with a similar idea in Edinburgh. "The governor of the time was a very enlightened man called Alex Spence," says Hoskins. "He believed that the penal system should make visitors feel comfortable and calm and not treat them like they were convicted criminals."

Spence realised that treating families with respect and consideration and creating an inclusive, common environment would foster a more beneficial atmosphere for the prisoners and diffuse the potential for distress and aggression. Hoskins's practice, which at the time was operating out of the spare bedroom of his west-end flat, duly came up with an innovative design which took account of the different kinds of people using the centre and their needs. "Obviously we had to think about families, so the emphasis had to be on children," he says. "Saughton is also a remand centre for young offenders, so teenagers were also a priority. We had to think of facilities, meeting places, storage, secluded areas to meet and talk, play areas, baby-changing, food, and, of course, a reception area for help and advice. It had to be friendly and welcoming."

The result is a bright, spacious building which uses natural materials such as granite, redwood, beech and cedar alongside steel, copper and glass. The main room has a high sloping ceiling with curved beams sweeping upwards, with separated seating areas and lockers on one side, sliding glass doors opening on an outdoor children's play area on the other, and a dining area in the centre served by a small cafeteria. There is also a meeting room, a TV room, a glass-roofed "drum" which houses a fussball table and comfortable seating, and an ingenious indoor children's area with a low-level window at kid height and a wooden wall dotted with tiny glass squares which at night look like stars from the outside.