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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

The Chesterfield Canal is a 46-mile-long navigable channel from the Derbyshire town of Chesterfield to the River Trent, passing through Staveley, Shireoaks, Worksop and Retford. The sections between West Stockwith junction on the Trent and Kiveton Park near Rotherham and from Staveley to just short of Chesterfield are navigable. The 10 miles from Norwood tunnel to Staveley are disused, Norwood tunnel has partly collapsed. The Chesterfield Canal trust plan to restore this section, but it requires a major diversion around Killamarsh.
The route is a typical James Brindley contour canal. An application was made to Parliament and the Act of Parliament received the Royal Assent on 28 March 1771. The canal was a success when it opened in 1777, however the Manchester, Sheffield and Lincolnshire Railway opened a parallel line in 1849. The last commercial traffic was in 1908.