In 1989 some of the building's finest rooms were converted to galleries for the Courtauld Institute of Art. More recently, other spaces were opened up to provide a new home for the splendid Gilbert Collection of decorative arts, the riverside terrace has become a summer café, and the central courtyard has been refurbished with fountains and a winter ice rink.

Since Nov. 25, 2000, another suite of handsome rooms has been reconceived as a U.K. outpost for the State Hermitage Museum in St. Petersburg, Russia. The installation is not without its high-tech touches. A visitor to the gallery is greeted with a screen showing a live televised image looking across Palace Square to the Winter Palace, the museum's home, continually zooming in and out on the façade. Another screen shows and re-shows a more conventional eight-minute tour of the Hermitage interiors.

Nearby, laptop computers are set up to access a database on the museum's 16,000 paintings, 600,000 prints and drawings, and 700,000 artifacts: Leonardos, Raphaels, Titians, the Attic red-figure vase showing reactions to The First Swallow, a late-17th-century Boulle cabinet, the 10-ft.-diameter Kolyvan vase made of jasper in 1843.

Beyond this general and relatively permanent introduction there will be more specific changing exhibitions. The first, on view until Sept. 1, 2001, is "Treasures of Catherine the Great." Catherine (1729-96) was hardly an endearing figure, having cuckolded, replaced and finally dispatched her royal husband, but she did much to establish the pride of the Russian people, and she did that partly through her accumulation of art. She was one of the world's great collectors.

The selection now in London opens with Poussin's Moses Striking the Rock, part of the Walpole collection that Catherine acquired (to British outrage) from Houghton Hall in 1779. There is also a set of eight architectural scenes by Charles-Louis Clérisseau, who served as a guide to classical ruins for both Robert Adam and Thomas Jefferson.

But the chief focus is on decorative arts. Hexagonal gold-framed vitrines hold miniature paintings, enamels, ivories, snuffboxes, jewelry, medals and Catherine's rather bizarre wig of silver threads. Other vitrines hold cameos, some of them dramatically backlit. Wall cases hold Sèvres dinner services, pieces from the Wedgwood "Green Frog" service made for Catherine in 1773-4, and products of the Imperial Porcelain Factory, St. Petersburg, where hard-paste porcelain was first produced in 1744. There is also a Wedgwood plaque attributed to John Flaxman, ca.1785, showing Catherine II Rewarding Art and Protecting Commerce.

Mantels hold porphyry and gilt bronze vases from the Yekaterinburg Lapidary Works, and work from the Tula Arms Factory is a striking show of artistry in steel with silver and gold inlay; it includes a toilet set, a chess set, a dressing table and a mirror. The last gallery touches on the Russian taste for chinoiserie and also features a 1770 surtout-le-table centerpiece of classical columns rendered in lazurite, jasper, marble, shell, silver and gilt bronze.

The exhibition offers only a small taste of Catherine's treasures, of course, and an even smaller taste of the Hermitage's. But it is a delicious taste and enough to make a powerful impression. Plans are reportedly underway for an even larger Hermitage presence in Amsterdam opening in 2005.