The enormous car park is almost completely deserted. It has enough space for hundreds of cars, but only a few stray vehicles are parked under the pale light of the street lamps. And save a handful of guests at the nearby pizzeria, there isn’t a soul in sight.

A cab? The waiter frowns as though he’d been asked an utterly absurd question. “After eight you can’t get a taxi anywhere in Gorizia.” Gorizia has called it a day.

“Give it a try over on the Slovenian side, they work round the clock in Nova Gorica,” he adds as an afterthought, and points to the sheltered border crossing, which everyone here calls Casa Rossa. “Look: that’s where the first shots of the Balkan Wars were fired in June 1991.“

The cars are whizzing past now without braking. The border itself has become invisible – and yet remains persistently present. Another world begins behind the Casa Rossa, in Nova Gorica – “New Gorizia”. On the left side of the road a big service station (“Open 0–24.00 hrs”) is doing brisk business, there is an outsized neon sign for the Casino Fortuna flickering on the right.

Everybody wants to hit the Perla, the biggest casino in Nova Gorica – its own ads say it’s the biggest in Europe. The lingua franca there is Italian, though when two croupiers chitchat you hear Slovenian. The euros switch sides ceaselessly, slipping out of the gamblers’ wallets and into the Perla’s coffers – and from Italy to Slovenia – around the clock.

The Italian town of Gorizia, on the other hand, won’t re-open till tomorrow morning at 9. The Via Rastello, a trim little lane lined with medieval buildings, is a sad sight: one shop after another for a 300-yard stretch, but three out of four of them are boarded up. “Happy Days,” promises the inscription on one awning, but the dirty windowpanes tell a different story, that those days are gone.

Marko Marini, in charge of “cross-border relations” for the province of Gorizia, agrees. The gaunt Green Party official speaks of opportunities passed up, how the opening-up of the border to Slovenia was more a loss than a new departure for this town. And that despite the fact that there was no border here for a thousand years, till 1947, when the new map of Europe was drawn after World War II. At the time the city lost virtually its entire catchment area to Yugoslavia – and took it well. The large, now inconsolably empty parking lot right at the border was originally for the Slovenes, who used to take daytrips through the somewhat permeable Iron Curtain to go shopping. “Paradoxically, the exchange between the two sides was a lot livelier then than it is now.”

Together, Gorizia and Nova Gorica could become truly European. But nothing is happening. A bus service connecting the two cities is the only development since the raising of the Iron Curtain.

Nova Gorica is young in comparison: none of its buildings is more than 60 years old. Tito raised the purpose-built town from scratch. The two dissimilar sisters could now become twin cities, says Miriam Bozi, head of Nova Gorica’s chamber of commerce, but since Berlusconi’s camp took Gorizia’s town hall in 2007, even she sees little chance of that happening now.

But the energetic business boss thinks big – alla grande. Nova Gorica has reported 6% economic growth per annum over the past few years. One mega-project has just gone down the pan, but no matter: Ms Mozi has already tabled the next scheme of really pharaonic proportions. “We want to erect a pyramid, bigger than the Cheops pyramid, two sides completely covered with solar panels, for a European aviation museum, investment volume €950 million,” she says, as if such a colossal project in this small town were the most natural thing in the world.

The last stop on the return route of the “International Bus Line” is the Piazza Transalpina. In the old days the border fence ran right across the piazza. This is where the big party kicked off on 1 May 2004 to celebrate the EU’s eastward enlargement, with then EU Commission President Romano Prodi as star guest. But Gorizia and Nova Gorica can’t even get it together here: on the Italian side the square is still called “Piazza Transalpina” – while the Slovenes have rechristened their half “United Europe Square”.