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Piccadilly Circus is a road junction and public space of London's West End, built in 1819 to connect Regent Street with Piccadilly.
Piccadilly now links directly to the theatres on Shaftesbury Avenue, as well as the Haymarket, Coventry Street (onwards to Leicester Square) and Glasshouse Street. The Circus is close to major shopping and entertainment areas in the West End. Its status as a major traffic junction has made Piccadilly Circus a busy meeting place and a tourist attraction in its own right. The Circus is particularly known for its neon signs mounted on the corner building on the northern side, as well as the Shaftesbury memorial fountain and statue, which is popularly, though mistakenly, believed to be of Eros. It is surrounded by several notable buildings, including the London Pavilion and Criterion Theatre. Directly underneath the plaza is Piccadilly Circus tube station.

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