By James Rodgers
BBC News, St Petersburg
The Hermitage Museum in St Petersburg, Russia, is famous as the palace of Empress Catherine the Great.
Generations of Hermitage cats have survived dramatic events
The greatness of its cats is the less well-known side of its astonishing story.
They have been here since the 18th Century. Fed up with rodents running through the palace, Empress Elizabeth sent out a decree that the best ratters in Russia should be sent to St Petersburg. The first to respond are thought to have come from the city of Kazan - then apparently famous for the rat-catching skills of its cats.
The cats survived the Napoleonic wars. They lived through the revolution of 1917. Their royal masters, Tsar Nicholas II and his family, died in a hail of Bolshevik bullets the following year.
As Russia turned communist, the cats kept their regal home.
They only disappeared during World War II. Hitler's armies laid siege to St Petersburg, then known by its Soviet name, Leningrad. Hundreds of thousands of people perished as for 900 days, the Nazis tried to strangle the life out of the city.
The most important items in the Hermitage collection were removed to storage in the Ural mountains, far from the front line. The museum's cellars became bomb shelters.
In peacetime, a new generation of cats was welcomed to the palatial surroundings their predecessors had made home.
Now, two full-time employees take care of them. Cosy corners of the Hermitage's cellars are their shelter in the depths of the icy Russian winter.
Maria Khaltunen sees the cats as part of the palace traditions
They are no longer chosen for their ability to catch rats. Poison has taken that job away from them. They have come here from the streets, and the Hermitage is happy for them to move on to good homes, where they can be found.
Officially, there are 50 of them. Museum staff make voluntary contributions to pay for their upkeep.
They are considered so important that they even have their own press secretary. Maria Khaltunen combines that role with her job as assistant to the museum's director.
While we spoke, one of her charges did its best to leap from her arms.
"We like them," she explained. "And all our staff decided to keep up this tradition: to have the cats, and to like them."
They may have retired from rat-catching, but a trip to the Hermitage's accounts department shows the cats are still there when a mouse is around. But these days, that's a computer mouse.
To be honest, the cats are more likely to be getting in the way than helping. Some have made their home with the book-keepers. They lounge across desks or curl up to snooze in open boxes of printer paper.
The Hermitage is one of Russia's major tourist attractions
They are not allowed in the galleries. But that does not mean they are cut off from the artistic atmosphere. Some of them appear perfectly at home among the statues in the Hermitage's gardens and courtyards - even occasionally seeming to strike poses copied from the classical-era art which surrounds them.