St Omer has a curious mixture of traditional Flanders red-brick townhouses and other of sandy stone, often within the same building. The presence of sandstone reflects its dim and distant origins as a port, although it is many hundreds of years since the harbour silted up and the sea is now 16km away. But its wealth from those years is visible everywhere, from the streets full of large townhouses and vast market square to the grand Gothic cathedral, complete with a painting by Rubens, and the ruined Abbey, destroyed in the French Revolution.
Becoming part of France in 1677 brought further aggrandisement, with the ornate Hôtel Sandelin created to house the Countess of Fruges and now the refurbished museum, and the vast Town Hall, built from the stones of the ruined Abbey despite the eloquent protests of Victor Hugo, who was supposedly inspired to write Les Miserables by his visit to this part of France.
During World War II this part of France paid a heavy price for its resistance to the Nazis - and also had a key role in the development of its weapons programme. La Coupole was a concrete dome created by Russian and Polish slave labour to launch, in secret, the V2 rocket on the enemy across the channel, created by scientists who became the architects of the space race on both sides. It is now a fascinating, and haunting, museum.
Access is one of St Omer's key selling points, and not just from Britain. Belgium is 45 minutes away, Lille is less and, by fast train, offers commutability to Paris. The nicer parts of the coast are half an hour away.
The city - one of the smallest in France, with only 16,000 inhabitants - was founded by Benedictine monks in the 7th century on high land above the river Aa. One of their most remarkable achievements was to drain the marshes around St Omer, creating an area of fertile farmland and beautiful watermeadows which is still home to dozens of families. These are mostly built with no foundations and gradually, over the years, they sink into the marsh, giving rise to endearingly wonky roofs and slanting walls.
Fortunately, the conventional property stock is more solid, with a good selection of traditional farmhouses, manor houses, cottages and townhouses. And the country is also not, as might be expected, flat, with green hills and woods alongside fields and rivers.
Peter Wilton, the St Omer representative for British agent VEFUK, is convinced that the motorway is both the reason for St Omer's obscurity and the means by which British visitors will finally begin to notice the area's attractions.
"It's a blink-and-you'd-miss-it turning off the main road south as you whizz by, one that too few people take," he says. "If they did, they would find a very attractive area full of interesting properties with prices considerably cheaper than more visited places such as Le Touquet, Berck and Boulogne.
"It is 20 minutes from Calais, so it brings easy access to British visitors. Cottages and farmhouses here, an hour's journey across the channel, are plentiful, and cost a third of something similar in southern England, and often have a similar look to a grand English country house or townhouse. With France having so much more space, they are also likely to come with plenty of land if required.
"Once the new Eurotunnel terminal opens in 2006, and access becomes ever quicker, I think that people will begin to explore the surrounding countryside and St Omer will begin to attract the attention it deserves."
What is striking is that the choice of property is as surprisingly wide-ranging as the scenery. British buyers tend to prefer houses of whatever size in their own grounds, although there are a number of elegant, four storey St Omer town houses for sale with pretty courtyard gardens. In a cobbled street near the market square is a white-rendered, 18th century townhouse with four bedrooms, wine cellar and gas central heating, for sale with La Residence for £110,000 (www.laresidence.co.uk, 01491 838485).
Just outside St Omer is a traditional long farmhouse, with outbuildings dating from every period since the 14th century, vast attics ripe for conversion, workshops and two newly refitted gîtes. A property with a huge square footage of residential space but without great tracts of land to keep up, it is clearly being marketed as an option for those looking for a home and business. The farmhouse is on the market with Europale in St Omer (03 21 95 98 98) for offers around £400,000.
Nearby, a village maison de maître, in Ouve-Wirquin, 20 minutes from St Omer, has Brit appeal stamped all over it. Complete with period features - so complete that a modern, functional kitchen might be a buyer's first move - and with scope for renovation yet with a new roof and well-kept exterior, it is large, elegant but with a manageable garden. Europale are marketing the house for £220,000.
Bruno Lemaire, who runs the Europale agency, is confident that the delights of his home town are already starting to become more widely known and says that business is brisk. "We have a number of good properties and there is certainly a lot of positive reaction. More British buyers do seem to be taking an interest in St Omer, particularly because it is so easy to reach the English south coast. If people take that turn off the road, they will see there is much here to admire."