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The A46 runs 24 miles from Enniskillen to Belleek, along the southern shore of Lower Lough Erne.
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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 Erne rises on the east shoulder of Slieve Glah mountain 3 miles south of Cavan in County Cavan, Republic of Ireland, and flows 80 miles through Lough Gowna, Lough Oughter and Upper and Lower Lough Erne, County Fermanagh, Northern Ireland, to the sea at Ballyshannon, County Donegal back in the Republic. The river is used for fly fishing for trout and salmon, with a number of fisheries along both the river itself and its tributaries. The town of Enniskillen is mostly situated on an island in the river, between Upper and Lower Lough Erne. It is linked to the River Shannon by the Shannon–Erne Waterway.