Ozeaneum is an architecturally dramatic extension to the existing Oceanography Museum in Stralsund, a town on the Baltic Coast.

Inside visitors can discover what is going on in a mysterious world that makes up 70 per cent of our planet's surface. The exhibition focuses, in particular, on the world's cold seas -- the North Sea, the Baltic and the Atlantic.

Only 2.4 square kilometres of the deeps have ever been properly surveyed, using submarine probes. Statistically that is so little that it barely even counts as a sample of the whole surface worldwide.

"We still don't even know about many species of creature in the deep oceans." said Harald Benke, director of the Oceanography Museum.

Striking shell for ocean treasures

The old museum occupies a former church. The 60 million euro ($95 million) extension could not be more different, comprising four rounded, steel-clad buildings joined by a glass foyer.

Although the structure nestles between ancient port warehouses and the whole town centre is a UNESCO world heritage site, NESCO has approve the modern-style Ozeaneum as an enrichment.

An architecture office from the German city of Stuttgart, Behnisch & Partner, designed the oval and kidney-shaped buildings, which give something of an impression of giant rocks rubbed smooth by glaciers.

A museum with green credentials

One display was paid for by the environmentalist lobby group Greenpeace, who invested 1.5 million euros to create full-scale replicas of seven whale species.

"We want visitors to see exactly what we will lose if whales become extinct," said Thomas Henningsen, who heads the Greenpeace project. The museum says the site contains the world's best library of whale books and data.

The live fish at Ozeaneum will live in the 39 aquarium tanks, which have a total capacity of 6 million litres. That is enough water to fill a bathtub 60,000 times over. To ensure it is disease free, it will come from the city water system and have 200 tons of salt added to make it similarly saline to sea-water.

Benke says the site is more educational than commercial aquarium attractions such as Sea Life at other Baltic Coast towns. It encourages children and parents to consider questions such as "Do fish drink?" or why the deep sea is such an extreme environment.

Ozeaneum also contains exhibits in old-fashioned glass cases and computerized displays. Benke says fellow museum experts have praised Ozeaneum's unique approach and hail it as one of the world's best aquariums.

Not everything has gone swimmingly

But the two-year construction project has been plagued by delays and budget over-runs. The biggest aquarium tank will have nothing but 2.6 million litres of water in it on Saturday because there has not been enough time to stock it with the schools of small fish which are to live there soon.

A planned penguin room and a tank for herring have not even been built because the project ran out of cash, even though 10 million euros was added to the original 50 million euro budget. By now, 52.6 million euros of taxpayer money has been granted to the project.

The museum is supposed to be self-supporting from now on, with at least 550,000 visitors annually needed to cover its running costs. Because much of the site will not be ready on time, entrance tickets will be discounted for several weeks.