Castle is fitting home for Beatty treasures

For years the Chester Beatty Library was Shrewsbury Road's well-kept secret, its treasures of rare books and manuscripts known to a small but appreciative group.

Its relocation to the imposing setting of the Clock Tower building in Dublin Castle will give the library the city centre showcase it deserves as a national cultural institution - and will open it up to the wider public in ways which might come as a shock to its scholarly curators. Sir Alfred Chester Beatty (1875-1968) was an American mining engineer, millionaire, philanthropist and connoisseur, with an eye for beautiful artefacts. He travelled extensively throughout the Far and Middle East in the 1920s and 1930s, collecting decorated manuscripts and miniatures from Japan, China, Persia, Egypt and India. He bequeathed his treasures to the Irish nation and was made an honorary citizen in 1957.

In addition to the main collection of decorated manuscripts on paper and vellum - including 1,259 manuscripts of Omar Khayyam - there are small sculptures, textiles, furniture, delicate Chinese snuff boxes and clay tablets from Babylon dating from 2,700 BC. To accommodate the Library's priceless collections the former Clock Tower building has been extended and fitted out with dedicated, state-of-the-art gallery spaces. Angela Rolfe is the architect in charge of the restoration and extension, for the Office Of Public Works.

The first phase of the £11 million project began in 1994. Built in 1756 and remodelled and extended in the early 19th century, the building is thought to have been designed by Francis Johnston, chief architect with the Board of Works from 1805-29. "We have restored the very imposing main staircase, which had been riddled with dry rot," Angela Rolfe says, as we tour the building. "The wooden clock tower has been restored and reerected, the moulded cornices of the interior have been reinstated and the chimneys have been rebuilt to their original height."

The restored building is linked to the new, enclosed exhibition area by glazed concourses, which feature raised walkways with bright blue railings. This light-filled, high-ceilinged space is the new public circulation area and entrance, with views across the garden of Dublin Castle and out on to Ship Street, to the rear. "We decided that the most important thing was to create a public space," Rolfe says. "People will be able to use the garden to wander in, have a look in the bookshop, have a coffee, enjoy the contrast between the enclosed wall of the old building and the bright glass space."

The extension is an enclosed "black box" structure, with a limestone base and brick upper storeys. Inside, the environment is very carefully controlled, with lighting, heat and air conditioning finely tuned to create optimum conditions for the fragile artefacts and to protect them from daylight. The original Chinese ceiling from the Chester Beatty Garden Library has been moved from Shrewsbury Road; the display areas have been divided into sacred and secular galleries.

The sacred gallery, displaying Islamic, Christian and Buddhist artefacts, has deep purple, green and red backgrounds. The secular galleries are lighter in tone and colour, and have a series of flexible screens. All the galleries have touch screens and audio-visual displays to help contextualise the exhibits.

ANGELA Rolfe is particularly pleased with the roof garden, designed as a room outside, an expanse of light after the darkness of the galleries. Tiny fibre-optic lights sway and blow on fine rods scattered through bamboo grass, and there's a trellis all around the roof garden with narrow slats giving views of Ship Street's yellow brick terrace.

"I think this is going to be a popular vantage point," Rolfe says. "A visit to the museum should be as pleasant as possible, regardless of people's level of interest in the exhibitions."

The Chester Beatty Library, Dublin Castle, opens on February 7th.