It is a little out of the way, but if you're a lover of classic art, you won't regret the trek to Dulwich Picture Gallery in South East London.
It holds the accolade of being the first public art gallery in England, opened in 1811. The initial collection, originally from Polish royalty, was bequeathed to Dulwich College by Sir Francis Bourgeois. To house this extensive collection, the College commissioned the architect, Sir John Soane (who's also the man behind the Bank of England and rooms in No. 10 and No. 11 Downing Street). The gallery Soane designed has come to be the archetype for art galleries across the world including the Getty Museum in Los Angeles.
Masters in the permanent collection here include British artists such as Thomas Gainsborough and continental heavyweights such as Rubens, Rembrandt and Canaletto. Paintings span the walls from floor to ceiling, sometimes making it difficult to inspect works closely. Take advantage of the central seating provided to study the works en masse as this is the best way to appreciate the more inaccessible paintings.
In addition to the permanent collection, the gallery runs a number of temporary exhibitions too. Upcoming displays include Desperately Seeking Conservation (October 13-January 3 2010), a group of paintings which are rarely displayed and are in need of restoration. In contrast, more modern work including watercolours and photographs by war artist Paul Nash can be viewed from Feb 10 - May 9 2010 in the exhibition Paul Nash: The Elements.
Keep an eye out for evening lectures and art classes that run at the gallery throughout the year. There's also a pleasant cafe and courtyard area to sit back and muse over one of the world's most unassuming, but inspiring, art gallety collections.