The Hermitage introduces their website with the following:
"The collection of the State Hermitage includes more than three million works of art and artefacts of the world culture. Among them are paintings, graphic works, sculptures and works of applied art, archaeological finds and numismatic material.
The main architectural ensemble of the Hermitage situated in the centre of St Petersburg consists of the Winter Palace, the former state residence of the Russian emperors, the buildings of the Small, Old (Great) and New Hermitages, the Hermitage Theatre and the Auxiliary House. The museum complex also includes the Menshikov Palace and the Eastern Wing of the General Staff building, the Staraya Derevnya Restoration and Storage Centre and the Museum of the Imperial Porcelain Factory."
The following is a description of the Winter Palace provided by the Hermitage:
The Winter Palace is the biggest building in the entire museum complex of the Hermitage. It was commissioned by the daughter of Peter the Great, Empress Elizabeth Petrovna, in 1754 as an official royal residence. Construction went on until 1762. The design was prepared by an outstanding architect of the Baroque style, Francesco Bartolomeo Rastrelli.
The three-story building occupies a whole block and amazes visitors with its grand scale and splendid ornamentation. The variety of impressions that the Winter Palace produces from different points of view is a result of the different compositional solutions of its facades. Though they share a common symmetry, they have different architectural forms and varying richness of plastic decoration. The whimsical shapes of the window and door casings, the splendid Corinthian capitals of the columns, the curved lines of sophisticated cornices, an abundance of statues and vases on the roof, and the festive colour of the walls lend a sumptuousness to the building which is characteristic of the Russian Baroque style.
The construction work on the Winter Palace was completed after the death of Empress Elizabeth Petrovna. The Palace was the official residence of the Russian monarchs from 1762 till February 1917 when the ruling dynasty of the Romanovs was overthrown in the course of the cout d'etat.
The most important events in Russian history were connected with the Winter Palace and its inhabitants. This is also where the Russian monarchs and members of their family led their private lives. The original palace interiors where the collections of the Hermitage Museum are housed today have not only artistic but also historical value."
The tourism website Saint-Petersburg entices us to visit, with this introduction of the Winter Palace:
Sprawling across the connected buildings of the Winter Palace, the Small Hermitage and the Old Hermitage, this vast, chaotic and incredibly rich collection is unquestionably the biggest draw for visitors to St. Petersburg. Founded by Catherine the Great, who bought up artwork en masse from European aristocrats, embellished by each of her successors, and then massively enriched by Bolshevik confiscations and Red Army seizures in conquered Germany, the Hermitage collection is incredibly varied, ranging from ancient Siberian artifacts to post-impressionist masterpieces by Matisse and Picasso. Equally impressive are the lavishly decorated State Rooms of the Winter Palace, testament to the incredible wealth and extravagant tastes of the Romanov Tsars.
Visiting this remarkable collection can be a daunting experience, particularly if you are not planning on booking a guided tour. With 350 rooms of exhibits and over 2.5 million visitors per year, the museum can be crowded and overwhelming. It pays to plan ahead to get the most out of your visit to the Hermitage and to ensure that you see the parts of the collection of most interest to you. To help you do this, we have split our Hermitage guide to cover each section of the exhibition separately, with details of the highlights in each section. One ticket covers all parts of the collection in the Winter Palace complex, except for the Treasure Galleries, which can only be entered as part of a guided tour. Separate tickets have to be bought for video and camera photography within the museum. It is also possible to pre-book tickets over the Internet, which is more expensive, but helps to avoid queues, which can be a problem for visitors during peak tourist season in the summer.
Wikipedia has an extensive article about the Winter Palace and it's substantial art collection.
For a history of the Hermitage and its many facets, visit Hermitage History