Vaska the cat, one of the Hermitage Museum mice hunters, seen in the museums yard, with an antic statue on the background, in St. Petersburg, in this April 25, 2004 photo. Cats have been part of the Hermitage’s security system since its founding days. (AP Photo/Dmitry Lovetsky)

Winding beneath the magnificent halls of St. Petersburg’s Hermitage Museum, with its Da Vincis, diamonds, Greek statuary, Egyptian parchments, enormous number of paintings, mechanical peacock clock, and other treasures, there is a catacomb of cellars. It was into this windowless nether region—far below the Winter Palace’s expansive view of the waters of the Neva—that Maria Haltunen and I had cautiously descended. As I followed her through a narrow, imperfectly-lit corridor, full of large pipes and jutting wires, Haltunen gasped. “Look!” she said.

In the semi-darkness, a little being had appeared. He perched, a foot-tall shadow, on a water pipe.

“Oh, you are a fat one!” said Haltunen, jangling the chain of her I.D. pass like a talisman as she approached the pointy-eared creature. “How nice you are!”

The cat sat, perfectly still. Then he vanished.