Crossing the border.

This lyrical, lightweight structure - part gate, part bridge - both marks and celebrates the crossing point from Italy into San Marino, one of Europe's smallest republics.

San Marino is a tiny republic within Italy, sited on the 700 m Monte Titano, a steep cone of a mountain near the Adriatic coast 24 km inland of Rimini. Settled in 310,(1) it became a republic in the thirteenth century, and has remained independent ever since, guaranteed its freedom by Napoleon and omitted from the unification of Italy. To the original hilltop settlement were added in Renaissance times a series of surrounding towns on the foothills known as the Castelli. Population is a mere 25 000, but the place has its own government (led by the Captains Regent, twin statesmen who are elected twice yearly) and thriving banking and tourist industries.

Giancarlo De Carlo was first invited to advise on the planning of the outskirts which has become an untidy sprawl, but discussion soon lighted on the problem of the boundary. Although the show of a police presence is maintained in daylight hours, frontier checks no longer take place, and the main road from Rimini, almost a motorway, had overwhelmed the brook which defines that edge of the territory. At 50 mph or more the roadside marker stone is imperceptible, and drivers could enter the Republic without noticing. The need was not for a physical gate but a means of letting people know the boundary is crossed. For De Carlo this was a fascinating problem, and he agreed to make a proposal. The idea was warmly accepted, quickly developed and built. The new Porta Dogana opened last July, the tape being cut by the two Captains Regent with two pairs of scissors. So popular is it that De Carlo has designed seven more gates on the lesser roads into the Republic which are currently under development.

The structure, of white-painted steel illuminated at night, is primarily a sign, an arch carrying the inscription 'Welcome to the ancient land of freedom', but it is also a flagpole and a footbridge. The footbridge fulfils a very real need for safe crossing of the busy dual carriageway, but it also allows people to dally there, to occupy the territorial edge and look down on the traffic beneath. It asserts the boundary line in opposition to the thrust of the road, and may become part of a frontier walk by the bank of the brook along which the inhabitants of San Marino might 'beat their bounds'.(2)

The flagpole sets a vertical accent, making the whole structure asymmetrical and provoking quite different treatments to the staircases on the two sides. It is the structural support from which the bridge is hung, the members sized and shaped in accordance with the loads transmitted. According to De Carlo this reflects a new view of structure in the computer age in contrast with most current practice which, he claims, is still dominated by the methods of the nineteenth century. Then designs had to be simplified to reduce the number of variables for ease of calculation, resulting in rigid repetitive structural forms. Now we can make calculations of enormous complexity very fast, predicting and adjusting the behaviour of complex asymmetrical arrangements.(3) In this case the structure was designed intuitively with a three-dimensional model, the sizes and precise positions of parts being adjusted by computer analysis. According to De Carlo there is a local fascination with technology, so this aspect should have some cultural resonance.(4)

The first impression is not altogether serious: slightly festive with something of the fairground about it, perhaps stressing the theatrical nature of the place and making the point that this is not a serious gate, not one which closes. It demands and repays exploration on foot, crossing and recrossing to look at the details - the complex suspension, the bowed wooden walkway, the glass 'eyes' in the cross ties designed by De Carlo and his daughter Anna. More obvious also is the intended reference to boats, in the swelling form of the walkway and the rigging above, which becomes more compelling in the lateral view. It is surely appropriate, for the road leads to Rimini and the sea, San Marino's main link with the outside world.

1 Legend has it that a Christian stonemason called Marinus fled to the mountain to avoid religious persecution by Diocletian. He worked a miracle cure on the son of a local noblewoman earning his canonisation, and in her gratitude she gave him the land where he founded a religious settlement in AD 310.

2 Beating the bounds was an annual ceremony in some English parishes, and consisted of walking the perimeter of the territory and making celebrations at certain points. Presumably in an oral culture this was the way of transmitting territorial possession.

3 This is a development of the ideas pursued in De Carlo's unbuilt tower project for Siena featured in Zucchi, Giancarlo De Carlo, Butterworth, 1992.

4 He cites the local car museum and particularly the collection of Ferraris, but there is also an older tradition of stone-cutting.