"You're from London and you're going to Kaliningrad?" a young man in Lithuania asked incredulously. "That's like me going to Mars."
The Kaliningrad region is one of Europe's strangest anomalies, a pocket of Russian territory separated, since the collapse of the Soviet Union, from the rest of the Russian Federation by Poland and Lithuania, now members of Nato and the EU. The region - 200 kilometres from east to west and a little over 100 kilometres from north to south - shot into the headlines recently after Russia announced that it would position rockets there in response to the eastward expansion of Nato's missile defence shield.
The capital, the former Prussian city of Königsberg, is also called Kaliningrad. Its grim reputation for crime, drug addiction and HIV is not enhanced by the unreconstructedly communist place names; while much of Russia has reverted to pre-revolutionary nomenclature, this has not been possible in a territory seized from the Germans at the end of the Second World War. But, the decrepit housing blocks and disintegrating cobbled streets notwithstanding, this is no longer a decaying outpost of the Soviet Union, but a gritty, energetic commercial city, with much new building and plenty evidence of economic activity.
Much of the historic centre was destroyed during the war or demolished in the decades that followed. The castle begun by the Teutonic Knights, which once dominated the city, was gutted by RAF bombing in 1944 and razed on the orders of Leonid Brezhnev in 1970, as a symbol of German imperialism. In its place was built the Palace of the Soviets, an ugly monolith that began to subside even before it was completed, and is known to local people as "the Monster". Its stained and rotting concrete shows through a recent forlorn attempt to improve its appearance by painting it sky blue.
Not quite all of old Königsberg has disappeared, however. From this bleak eminence, you can look down at the cathedral on its island in the River Pregolya. A hollow shell throughout the Soviet era, it has now been restored to medieval gingerbread splendour with financial assistance from Germany. Prospekt Mira is still lined by handsome neoclassical façades, and the inner ring road is punctuated by a series of turreted, 19th-century forts. Beyond the city limits is an outer ring of 15 forts, built after the Franco-Prussian War, in part by French prisoners of war. Less visible and seldom visited, they have been used for the past 50 years to store vegetables, and are slowly crumbling. Most are dangerous, and some are still surrounded by unexploded mines.
But Fort No 1 (Fort Stein) is looked after by an unpaid caretaker who lives in the fort itself with his family. I drove out there one afternoon with my interpreter, Lydia, to visit him. The polygonal fortification stands on a low tree-covered hill, amid neglected farmland to the east of the city. It covers the road from Kaunas, from where it was assumed a Russian advance would come - as indeed it did in August 1914 - and is surrounded by a deep, dark moat, which you cross by a drawbridge, surrounded by gun embrasures.
Stanislav Laurushonis, a tall, wiry man in his mid-forties, opens the enormous iron door and greets us. He first came here in 1991, when a co-operative, known as the Old City, was set up with the aim of raising money to restore surviving historic buildings. The Old City rented the fort from the organisation that stored vegetables and grain there. Then, with the help of volunteers, it started to restore the building.
When Stanislav was evicted from his flat, he simply moved in here, and has squatted the place for the past 14 years. His office occupies one of the barrack rooms; he and his family live in another. There is no running water except for an old well, no heating except for wood-burning stoves, and if they need electricity, he must cycle to the nearest filling station with a jerrycan to fuel the generator. This has not stopped the electricity and water companies from presenting him with huge bills.
"The officials who made out the bills knew perfectly well that we have no mains water or electricity," Stanislav explains. "They just expect you to pay a bribe. One day they'll probably take the building and we'll be on the streets."
We walk down the long, dark, sloping central tunnel to a flooded gun emplacement. To either side are rooms for officers, barracks, a hospital and a telegraph station. The total garrison, during periods of mobilisation, numbered 250. In one of the barrack blocks is an array of artefacts recovered from the site: rows of German helmets, rusting sub-machine guns, bayonets, horseshoes, mess tins and a field telephone. A 200-litre oil drum is stamped with the date 1943 and the warning: "Inflammable. Wehrmacht".
A glass-fronted bookcase sits along one wall of the office; on the others are maps, photographs and charts. In the bookcase are some smaller artefacts: cartridge cases, a dagger and an aluminium belt buckle with a swastika surrounded by the words "Gott mit uns". I translate. "The Devil was with them!" hisses Lydia.
Stanislav has a powerful sense of mission: to preserve the memory of the soldiers - Russian and German - who fell here. He holds a commemorative service every year on 9 April, the anniversary of the fall of Königsberg.
"People say to me: 'Why are you trying to preserve this? It's a German monument.' But if you want to live in peace, you must preserve these monuments. Anyway," he adds, "they are no better when it comes to Russian monuments."
We emerge on to the gun platform on top of the fort, which is grassed over, with trees growing from it. An amphitheatre in the centre - originally a drill square - is now used for occasional musical events. The eerie ambience makes it a magnet for bikers, Goths, neo-pagans and "dark folk" bands. Even shamans from Siberia have performed here.
"Do you know Tarkovsky's film Stalker?" Stanislav asks as we are about to leave, and somehow I understand what he is saying before Lydia has time to translate. In this haunting film, the Stalker ekes out an existence guiding visitors into a mysterious Zone, cordoned off by the military, in which the normal rules of physics do not apply. "This is the Zone," he says, gesturing around us.