I invite you to the Hermitage State Museum.
The Hermitage Museum is Russia's best gallery of world art, one of the most prominent art museums in the world and definitely the main tourist attraction of St. Petersburg. The museum was founded in 1764 when Catherine the Great purchased a collection of 225 paintings from the Prussian merchant . Today, the Hermitage houses the collection of about 3 million exhibits and displays a diverse range of art and artifacts from all over the world and from throughout history (from Ancient Egypt to the early 20th century Europe). The Hermitage's collections include works by Leonardo da Vinci, Michelangelo, Raphael and Titian, a unique collection of Rembrandts and Rubens, many French Impressionist works by Renoir, Cezanne, Manet, Monet and Pissarro, numerous canvasses by Van Gogh, Matisse, Gaugin and several sculptures by Rodin. The collection is both enormous and diverse and is an essential stop for all those interested in art and history.
The main building of the Hermitage Museum is the Winter Palace, which was once the main residence of the Russian Tsars. Magnificently located on the bank of the Neva River, this green-and-white three-storey palace is a marvel of Baroque architecture and boasts 1,786 doors, 1,945 windows and 1,057 elegantly and lavishly decorated halls and rooms, many of which are open to the public. The Baroque Winter Palace was built between 1754 and 1762. Many of the palace's impressive interiors were remodeled after the huge fire that partly destroyed the building in 1837. Some of the best Russian and most famous foreign architects worked there to ensure that this Imperial residence was one of the finest and most luxurious palaces in the world.
The Hermitage's collections are displayed in adjoining buildings along the Neva embankment, together form an enormous museum complex: the Winter Palace, the Small Hermitage, the Old Hermitage and the New Hermitage. The Hermitage Theater, the private theater of the Tsars, is a beautifully decorated amphitheater and still hosts regular lectures, concerts, opera and ballet performances.
If you spend a minute looking at each exhibit on display in the Hermitage, you will stay there for 7 years before you see them all.
I suggest you opt for a guided tour instead!