By Jorn Madslien BBC News business reporter at the Geneva Motor Show

The curtains go up officially on the Geneva Motor Show on Tuesday - but many of the carmakers' most important releases have already been revealed.

The covers are still on, but many of the secrets are out

Across the city on Monday night, the big firms threw a series of plush parties to give a "sneak peek" at their new models.

Among the most lavish previews was BMW's press event at Geneva's plush Batiment des Forces Motrices, the huge dance theatre where the car maker's latest 3-series model was unveiled.

Photos of the discreet-looking car were leaked as early as last August and BMW has been arranging test drives of the car throughout winter.

The only unknown about the model, therefore, is how it will be received by car buyers and what its impact will be on the Bavarian firm's bottom line.

BMW is betting on it being a best-seller, and aims to build 350,000 3-series cars this year.

BMW also revealed plans to move further into the area for car-like crossover vehicles in the belief that both traditional models and mini-vans have had their day, chief executive Helmut Panke told BBC News.

Made in Germany?

Near the BMW event, Bentley offered a sneak preview of its four-wheel drive Flying Spur, the four-door version of its Continental grand tourer, at an equally lavish event.

There was much talk about the marque's racing heritage and its British roots - along with a stiff rebuttal of rumours that the car is to be produced at parent Volkswagen's factory in Dresden.

Bentley's new Flying Spur comes close to 200 miles an hour

"Dresden is a city in North Germany; we are going to be producing it in Crewe," Bentley chief Franz-Josef Paefgen said.

The company would not, however, rule out the option of producing some Continentals in Germany as an overflow solution should demand for the car warrant it.

Just a few blocks away, Mazda revealed its third-generation MX-5. The MX-5 has been one of the world's best-selling roadsters, and Mazda is hoping this slightly more spacious version will cement its pole position.

Alfa's new cousin

The beleaguered Fiat group is also hoping to make a splash this year.

Open for the public from 3 to 13 March The centenary of the "First National Motor and Cycle Show" organised in Geneva in 1905 The 75th international event since 1924

Ferrari's Superamerica, first shown to the Americans in January, makes its European debut at a time of considerable upheaval for the company.

Last month, the Maserati marque was separated off from Ferrari - now to be blended with the Alfa Romeo marque under the watchful eye of former Rolls-Royce chief Karl-Heinz Kalbfell, the BMW Group executive who was poached by Fiat last October.

Alfa Romeo is also making a splash with a long overdue update of its model range. The hope is that its Brera and its 159 models will help bring back customers to the struggling marque.

Fresh challenge

Among the French launches at this show, there is Citroen's C6.

A luxurious if low-key alternative to traditional choices such as BMW and Mercedes, its high-tech gadgets may well make it a successful niche model, though there are doubts that it will become more than that.

Renault will also be making a splash with its Z17 concept car.

On the face of it, its design - with just three seats - feels odd.

But it is not alone: Volvo, too is offering a three-seater concept car called the 3CC which

Will three seats be enough for Volvo's concept car?

will make its European premiere here in Geneva.

Aston Martin , Volvo's sister-marque within Ford's Premier Automotive Group, is unveiling its V8 Vantage, a car it hopes will sell to the tune of 5,000 a year despite a price tag of more than 100,000 euros.

The Ford subsidiary insists Porsche, which will unveil two 911 convertibles, should be worried.

Convertible Colt

General Motors will make further efforts to sell US marques to Europeans with its BLS baby-Cadillac and by further pushing its Chevrolet Europe model, which it makes together with Daewoo of South Korea.

Its European subsidiary Saab will unveil a sporty estate version of its 9-5, while sister brands Opel and Vauxhall will display a new version of its Zafira seven-seater and an Astra concept with a diesel hybrid engine.

Fast-growing Asian carmaker Kia is here with a medium-sized car specially designed for the European market, while Hyundai will show off a competitor to the luxurious Toyota-subsidiary Lexus.

Also edging further into the luxury sector is Honda with its latest Civic model, while Ford is remaining distinctly folksy with its launch of a "sports activity vehicle" - a smaller five-seat version of its Galaxy seven-seater.