Thick Galway limestone was used in the €21m Department of Finance building, but the placing of windows and natural ventilation lets the building shine and breathe

SPIKE MILLIGAN will rest easy now, in the confident knowledge that the Huguenot cemetery at Merrion Row, Dublin, will never fall into the hands of developers. Years ago, fearing that it was under imminent threat, he wrote me a letter almost demanding to know what I was going to do to save this unique place in the heart of the city.

He had got his wires crossed, however, and I wrote back assuring him that the cemetery was safe. Since then, it has been visually opened up by a set of railings - a project carried out sensitively by Nick Sutton, now a director of HKR Architects - so passers-by can see the profusion of bluebells that cover it like a carpet every spring.

The cemetery, opened in 1693, is believed to be the oldest Huguenot graveyard in Europe. And it can never be redeveloped now because the trust that owns this little plot gave its consent to the placing of windows in the west elevation of the superb new building next door, designed by Grafton Architects for the Department of Finance.

Previously, the 1970s office block that stood on this site had a blank redbrick wall facing the cemetery. But the new building has windows on every floor, some flush with the façade and others recessed, in a modulated composition that was intended to address the city as well as show due deference to the Huguenot dead.

As the architects say, the building is "rooted in its immediate urban context", relating to the grandeur of St Stephen's Green, the "secret garden" of the cemetery and the streetscape of Merrion Row.

It is also "pulled back" from the graveyard, separated from it by a solid wall of Kilkenny limestone, which was flamed to give it a darker hue.

The building is also pulled back from the street at ground level, with a 3-metre cantilever two storeys above the entrance, a "bridge" over the basement area, a bronze gate and railings. This arrangement was inspired by Georgian houses on St Stephen's Green, with their setbacks, low walls, railings, steps and basement areas.

The setback also brings light into the lower ground level, which would otherwise have been quite dark. Reflective metal-reveals to each window above also continues the Georgian technique of "bouncing light deep into their rooms by making windows reveals of white-painted plaster in their flush brick façades", as Grafton say.

Indeed, the building is extremely fortunate in having windows that face north, south, east and west. The layout is also highly unusual, because all circulation is at the perimeter - as in Sam Stephenson's iconic Central Bank - with all the office space in the middle, enjoying views out through floor-to-ceiling glazed screens.

Its tour de force internally is the staircase, which occupies the Merrion Row frontage, winding up initially through the lower part of the building before changing dramatically into a grand staircase suspended within the largest volume. Made from light oak, it acts as a screen to the south sun as well as an acoustic buffer from the traffic.

The staircase is woven into the design, offering the possibility of chance conversation and discussion while overlooking the life of the street. To the rear, there are fine views from the top floor of Government Buildings and the rooftop helicopter pad which Charlie Haughey had installed when the complex was renovated in 1991.

The façade to the Huguenot cemetery was designed to give maximum light to the offices and maximum privacy to the cemetery. "It's a stone screen that has depth," says Grafton's Yvonne Farrell and Shelley McNamara. "The stone is crafted to feel like stone - not hung on to the façade like slices of white bread, but built by experienced masons."

It is 450mm - nearly half a metre - deep, made from 100mm thick "planks" of light grey limestone from the quarry in east Galway. It looks like a solid block of stone, with cut-outs for windows either fixed and flush with the façade, or recessed and sliding. Thus, there is a permanent connection for those within with the city outside.

The jagged lines of windows have "nostrils" beneath to draw in fresh air which is then distributed into the offices. Stale air is drawn up into six "chimneys", placed centrally in the plan. These are clad with glass fins, but are meant to evoke the bank of chimneypots protruding above the roof of a Georgian house, like the one just down the street.

The building's scale lowers as it adjoins its neighbouring property, forming a strong end-piece to the existing terrace on Merrion Row with a section that takes up the height and width of a typical Georgian house, before rising to six storeys to address the scale of St Stephen's Green, notably Huguenot House and the Shelbourne Hotel.

What marks it out from its neighbours is not merely a great presence in the streetscape, but the subtlety of its architecture.

Thus, the grey stone façade to Merrion Row incorporates thin 20mm reveals to create shadows on sunny days; this incredibly clever little detail was intended to relieve the impression of a monolithic stone block.

Beyond the entrance lobby is a glazed zone leading to The Billets, a long two-storey mews-type building from the early 20th century that was used to accommodate soldiers guarding Government Buildings - the last major project in Dublin built under British rule. A tunnel beneath the internal roadway links it with the Department of Finance.

Offices occupy the lower level of The Billets while the upper floor, with its exposed metal trusses and dormer windows, has been converted into conference rooms and a tranquil staff canteen lit by large lamps.

Dolphin's Barn brick walls, with beautifully detailed granite corbels to carry the trusses, have been left exposed in their natural state.

Incredibly, the new building on Merrion Row is the first purpose- built offices for a Government department since Agriculture House on Kildare Street was built in the early 1970s by Stephenson Gibney. But its ambition is much closer to the heroic scale of the State's first office building directly opposite, designed by Boyd Barrett in the 1930s.

Grafton worked closely on the project with senior Office of Public Works architects John Cahill and Ciarán McGahon, who are both thrilled by the result. The OPW's promotion of a more open-plan culture is also evident in the layout, with only senior management getting their own offices, separate from lower-ranking members of the 170 staff.

Such bespoke buildings do not come cheap. The construction budget for Merrion Row came to €21 million, or €6,254 per sq m - significantly more than spec-built office space. Officially opened by Brian Cowen on May 6th, on his final day as Minister for Finance, it has been made to last - a building not just for our own time, but also for posterity.