Tickets to see Wagner's epic Ring Cycle lasting 19 hours over four days at the Wales Millennium Centre have sold out in just four hours.
The Wales Millennium Centre opened in Cardiff in November 2004
Fans from across the world have bought seats costing as much as £750 for the performance by Russia's Mariinsky Theatre - formerly the Kirov Opera.
The shows in December will be their only planned UK performance.
Tickets have gone to fans as far away as Russia itself, as well as the USA, the Middle East and France.
The capacity of the Cardiff venue has had to be reduced from 1,900 to 1,650 because of the size of the orchestra needed to play Wagner's music.
Tickets went on sale at 1000 BST on Monday, and had all gone by 1400 BST. The cheapest were £80, while the top price of £750 buys a so-called "superseat" which will include a champagne reception with the cast.
Among the few lucky enough to buy top price tickets are retired patent attorney David Mere and his translator wife Kathleen, from near Berne in Switzerland.
The couple have not visited Wales Millennium Centre before, but they are certain that the trip will be value for money.
"Someone told me the other day the Millennium Centre is absolutely fabulous and we're greatly looking forward to it," said Mrs Mere.
"Some people think paying £100 to watch football is value for money - for us £750 to watch the Ring Cycle is not expensive.
"It's rare to get a chance to see the four operas in four consecutive days with a large enough ensemble for key cast members to be able to rest between performances.
"One works hard and one spends one's money on the things one loves," she added.
Millennium Centre chief executive Judith Isherwood said: "We always expected to sell out the Ring Cycle.
"But we have been absolutely thrilled that it sold out so quickly.
The cycle is described as a mythical masterpiece'
"It is hugely exciting for us and will undoubtedly consolidate Wales Millennium Centre's place on the international cultural map."
Mariinsky director Valery Gergiev visited the centre when it was being built, and returned to Cardiff in April 2005 with the Mariinsky Ballet, formerly known as the Kirov Ballet.
Mr Gergiev, who will conduct all the performances, which will run from 30 November - 3 December.
Fiona Allen, programming director of the centre, who saw the Ring Cycle in Moscow last year, said: "Very few venues have the technical capability to present a production of this scale.
"Seeing the enormity of the production in Moscow, I realised that WMC is one of the few theatres in the entire world in which it could be performed."