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Dulwich Picture Gallery is an art gallery in Dulwich. The gallery, designed by Regency architect Sir John Soane using an innovative and influential method of illumination, opened to the public in 1817. It is the oldest public art gallery in England and was made an independent charitable trust in 1994. Until this time the gallery was part of Alleyn's College of God's Gift, a charitable foundation established by the actor, entrepreneur and philanthropist Edward Alleyn in the early-17th century. The acquisition of artworks by its founders and bequests from its many patrons resulted in Dulwich Picture Gallery housing one of the country's finest collections of Old Masters, especially rich in French, Italian and Spanish Baroque paintings and in British portraits from Tudor times to the 19th century.
The Dulwich Picture Gallery and its mausoleum are listed Grade II* Link
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Listed buildings and structures are officially designated as being of special architectural, historical or cultural significance. There are over half a million listed structures in the United Kingdom, covered by around 375,000 listings.
Listed status is more commonly associated with buildings or groups of buildings, however it can cover many other structures, including bridges, headstones, steps, ponds, monuments, walls, phone boxes, wrecks, parks, and heritage sites, and in more recent times a road crossing (Abbey Road) and graffiti art (Banksy 'Spy-booth') have been included.

In England and Wales there are three main listing designations;
Grade I (2.5%) - exceptional interest, sometimes considered to be internationally important.
Grade II* (5.5%) - particularly important buildings of more than special interest.
Grade II (92%) - nationally important and of special interest.

There are also locally listed structures (at the discretion of local authorities) using A, B and C designations.

In Scotland three classifications are also used but the criteria are different. There are around 47,500 Listed buildings.
Category A (8%)- generally equivalent to Grade I and II* in England and Wales
Category B (51%)- this appears generally to cover the ground of Grade II, recognising national importance.
Category C (41%)- buildings of local importance, probably with some overlap with English Grade II.

In Northern Ireland the criteria are similar to Scotland, but the classifications are:
Grade A (2.3%)
Grade B+ (4.7%)
Grade B (93%)

Read more at Wikipedia Link