This Europe: Giant glass cocoon set to descend on home of the Kirov

A French architect has won an international contest to modernise St Petersburg's 19th-century Mariinsky Theatre, once the Kirov, with a giant glass and marble cocoon.

Dominique Perrault, creator of the glass-and-steel National Library in Paris, led one of 11 teams taking part in a competition to design the first big work of modern architecture to be built in Russia's imperial capital. The project, chosen from a range of ultra-modern structures and more conservative Russian designs, envisages a black marble building cloaked in a translucent casing of gold-coloured glass. It will be linked to the main theatre by an extendable bridge.

Perrault told a news conference on Saturday: "The idea is ... that a great opera should be an emblematic building that is visible in the city. The golden envelope is the symbol of all the great monuments of St Petersburg. The second idea is to open the opera: everyone can come in, wander around, walk through the opera along the canal."

The £60m opera and ballet auditorium will give fresh impetus to the celebrated theatre, once home to the dancers Anna Pavlova and Rudolf Nureyev, but now suffocating in a 19th-century building it has outgrown. A severe lack of space forces the theatre to close down for days while rehearsing new productions. Valery Gergiyev, director of the Mariinsky, said: "We continue to love our theatre more than any other. But we have long ago noticed that for us to work as a modern theatre we have very difficult hurdles to overcome."

The contest to pick a design for the new 2,000-seat venue, intended to combine modern design with the city's 19th-century architectural heritage, excited much debate. Critics feared the additional structure, due to sit alongside the elegant green original theatre, would shatter architectural harmony.

Mr Gergiyev initially picked an outlandish design by the US architect Eric Moss - known to its critics as "garbage bags" - but was forced to back down and call an international contest.

Five competitors from Russia and others from Austria, France, Japan, the Netherlands, Switzerland and the United States eventually submitted proposals, including Moss.

Originally named Mariinsky after Maria Fyodorovna, wife of Tsar Alexander II, the theatre was known in Soviet times as the Kirov in honour of a Bolshevik leader. It later reverted to its old name.

The new venue should be completed by 2007. It includes a plan to span the adjacent Kryukov canal, one of dozens of canals in the city, which was built on marshes by Peter the Great.