A unique exhibition, built around a single painting of the Old City of Jerusalem, has opened in the Chester Beatty Library at Dublin Castle with the hope of bringing together the three monotheistic faiths for which the city is sacred: Judaism, Christianity and Islam.

Jerusalem, The Eternal City, a 10-square-metre painting by Ben Johnson, has given its name to the exhibition, which also includes 40 modern and archival photographs illustrating the religious and cultural diversity of the city and its rich 4,000-year heritage. Dr Michael Ryan, the director of the library, describes it as "a non-denominational exhibition about an extremely denominational city".

Johnson's realist painting, first exhibited at the Royal Academy of Arts in London last year, was commissioned by the Khalili Family Trust in "the hope that in the new millennium it will be possible for Jews, Christians and Muslims to live together in peace and harmony".

It was a mammoth undertaking: more than four-and-a-half metres long and two-and-a-quarter metres high, it covers a wall of the exhibition area. The work has a photographic quality, is painted in acrylic and took three years to complete. And, as he worked, Johnson used 60 litres of paint, 8,000 scalpel blades and 24 miles of masking tape.

Architecture provides the focus of Johnson's work. The only artist to have been made an honorary fellow of the Royal Institute of British Architects, his previous works include Hong Kong Panorama, another city view, commissioned to mark the return of the British colony to China, and The Rookery, providing a close interior view of Frank Lloyd Wright's Rookery building in Chicago.

Johnson's painting provides a bird's-eye perspective of the city, giving the viewer a detailed look at 20,000 buildings, each painted to scale. "I wanted the painting to represent the truth of Jerusalem: the proximity of the three faiths and the exact proportions of the city," he says.

He has painted Jerusalem as everyone's holy city, a universal symbol of hope. But he provides a view that no visitor or pilgrim can hope to experience. The city is painted from an imaginary height to the west of the New Gate and David's Citadel, inviting the viewer to look east across the city and out to the Mount of Olives.

Beyond, the new Jewish settlements in East Jerusalem, the focus of so much controversy and conflict today, are a blur to the point that they might have been airbrushed out of the picture.

The light of the setting sun casts gentle shadows across Johnson's painting, so that the eye is drawn back continually to the city's three most significant religious sites. For Muslims, the Dome of the Rock commemorates Muhammad's ascension to heaven; for Jews, it is where Abraham prepared to sacrifice his son.

The dome's size, position and colour mean it dominates other images of Jerusalem, but the light in Johnson's painting forces the eye to give equal attention to the Western - or Wailing - Wall, the last remnant of the Second Temple of Jerusalem, and to the Church of the Holy Sepulchre, which is built over the tomb of Christ.

It is an idealised image of Jerusalem: there are no satellite dishes, there are no television aerials and there is no traffic. But if there is no traffic, there are no military roadblocks and checkpoints, and if there are no controversial settlements beyond the city, then there are no people in the city either.

I once asked a west-of-Ireland rector what his parish was like. "Oh, it's fine," he replied, rakishly. "It's the parishioners that have the problems." Jerusalem would also be at peace without its people, of course, but the viewer must ask what sort of peace it would be.

Controversy within the religious traditions has been carefully painted out, too: the Tomb of the Virgin, which few Irish pilgrims will have heard about or visited, is missing from Gethsemane, and so a point of controversy among Christians and between some Christians and Muslims is creatively avoided.

The painting has been reproduced in map form, with 60 prominent sites identified so visitors can locate them in the painting. Members of the public are being invited to write down their thoughts on how people can live together in peace and harmony, and a selection of comments form a part of the exhibition.

According to Dr Elaine Wright, the curator of the Islamic collection at the Chester Beatty Library, the exhibition offers "an invitation to each visitor to pause and take time to explore for him or herself ways in which people everywhere might learn to live together in our religiously diverse world, whether in Jerusalem, here at home in Ireland or anywhere else."

The 40 photographs illustrating Jersusalem's religious and cultural diversity are drawn from the collections of the Royal Geographic Society, the Palestine Exploration Fund and private collections in Britain and Ireland, including the Patrick Boylan Collection in the department of Near-Eastern languages at University College Dublin.

Among the historic photographs is one of the al-Aqsa Mosque taken by Captain Arthur Rhodes on December 14th, 1917, five days after Allenby captured the city.

The Khalili Family Trust, which is also providing financial support for a lecture series that is running until November, was set up by Nasser David Khalili.

Dr Khalili, who also chairs the Maimonides Foundation, a forum on peace and understanding for Muslims, Jews and Christian Arabs, was honoured in 1996 with the title of Trustee of the City of Jerusalem for his "pursuit of culture and peace among nations".

Jerusalem, The Eternal City continues at the Chester Beatty Library, Dublin Castle, until November 25th; further information is available from the library's wesbite, at www.cbl.ie

Patrick Comerford is an Irish Times journalist and a Church of Ireland priest. E-mail: theology@ireland.com