But the lure of high-wire acts, slapstick clowns, lion tamers, dancing elephants and exotic beasts for modern audiences is being eclipsed by the trend-setting innovations of the Cirque du Soleil.

Behind the scenes at Moscow's Nikulin Circus, spinning acrobats and a juggler on a unicycle practice amid a cacophony of music and raised voices. A big grey elephant calmly awaits a turn in the ring. The stench of the menagerie is overpowering.

"It's getting harder to impress people," complained Yulia Silantyeva, a big cat trainer, who comes from a large family of big top performers. "It (the Russian circus) is losing its strong standing."

Under the Soviet Union, Russian circuses held a stature on a par with its globally renowned opera and ballet, touring internationally and boasting of visits from the Russian elite, including Soviet leader Leonid Brezhnev, whose daughter ran off with a circus acrobat at 22.

"Brezhnev was the country's last leader to visit the circus... This is not the attitude the circus deserves," said circus manager Maxim Nikulin, who followed in the footsteps of his father, Yuri, a beloved and world-renowned clown and actor whose portrait graces a Russian stamp.

As prestige has faded and state support dried up, the best performers have moved abroad, in a run on talent akin to the so-called brain-drain of scientists and engineers who have also deserted mother Russia.

Many performers have defected to the Montreal-based Cirque du Soleil -- the new gold standard in acrobatic arts.

Russians now make up about 35 percent of the Cirque du Soleil's 1,200-person crew of artists. Talent from other post-Soviet states also make up much of its troupe.

MY DREAM

Russian acrobat Ruslan Yakimolin, dressed in a unitard during a rehearsal for one of the Cirque's shows, trained at the Moscow Circus but said he had not a moment's hesitation when le Cirque invited him to move to Canada two years ago.

"It was always my dream to join the Cirque du Soleil, they invited me and now I'm here," Yakimolin said, catching his breath following a series of daring somersaults.

The 27-year-old Cirque du Soleil came to Moscow with its first show just three years ago, but already Russia is its fastest-growing market.

The mega circus is two weeks away from launching its most expensive production ever, a $57-million extravaganza entitled Zarkana, at Moscow's Kremlin Palace.

The venue itself is monumental: Built on the orders of Soviet leader Nikita Khrushchev and used for Communist party congresses, it is a 6,000-seat theatre inside the Kremlin walls.

Zarkana will command the space for more than three months -- much longer than most typical theatre and dance shows.

"We have had four shows in Moscow in 27 months, that's the quickest expansion of Cirque du Soleil anywhere in the world in the last 10 years," Craig Cohon, co-founder of Cirque du Soleil in Russia, told a press conference on Wednesday.

"There is a huge opportunity here," he said.

The outfit, founded by former circus performer turned billionaire and space tourist Guy Laliberte, is expected to decide in April whether to open a permanent show in Moscow.

But Cohon rejects suggestions that Cirque du Soleil is stealing viewers away from the traditional Russia circus -- not least because tickets to its show are four times as costly as Nikulin's performances, whose cheapest tickets go for $13.

"It's a completely different type of entertainment," he said.

Despite the richness and special effects of the Cirque's luxurious adult shows, Nikulin's performers say animals, clowns and other traditional acts will continue to have the power to captivate children.

"Cirque du Soleil clearly attracts the best talents from the local circuses and many leave," said Silantyeva, whose boyfriend has been recruited to the Cirque du Soleil.

"But the Russian circus, Russian animals, Russian clowns remain. They are something viewers are used to and what our circus is world-renowned for."

(Additional reporting by Jennifer Rankin; Editing by Alissa de Carbonnel)

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