Also known as the "Mykelldiche" ("Great Ditch", Middle Eng.). Except most people don't give it any name or any thought at all.
It's around 6 miles (almost 10Km) long and runs roughly East-West between the River Mersey to the south and the River Medlock to the north.
Nobody knows how old it is, but it is first mentioned in a land title document in the year 1200. Some theories say that it was probably excavated as a defensive earthwork during battles with Danish invaders around 800-900AD. This is a reasonable theory. We have evidence that these battles took place and that the native inhabitants of the area immediately north of the ditch eventually successfully repelled the invaders after much bloodshed and destruction. However, the ditch originally had a U shaped profile, more usual in a boundary marker or agricultural drainage ditch. Defensive ditches usually had a triangular V shaped profile, and are considered easier to dig in a hurry. So why would Dark Age homestead defenders dig a U shaped ditch to ward off Danish invaders? We may be missing something here. There is no authoritative final answer, which is one of the reasons I like this ditch.
Nobody can definitively date it, it could be much older than 800AD. Historic England, a public organisation charged with administration of such matters, has designated stretches of the ditch as a historic monument of national significance (whatever that means). HE has suggested that the ditch may be the oldest surviving geographical evidence of human habitation in the Manchester region. Historic England also confidently asserts in the official list entry for the ditch that because it has (more properly, had) a certain kind of name and a spatial relationship to Anglo-Saxon settlements, it must therefore be of Anglo Saxon origin. I quote;
"The facts are that it forms a demarcation between an area of low-lying ground between two mosslands to the east and west of the site of the Anglo-Saxon town of Manchester, that it forms a boundary between several medieval townships along its length and that its name is firmly Anglo-Saxon in origin. This means that it was constructed during the administration of the Anglo-Saxon kingdoms between AD 600 and the tenth century."
This is, in my opinion, extremely careless thinking. Any ditch predating the Anglo Saxon era, would come to have an Anglo Saxon name as the area was resettled. The ditch may have had one hundred names from its origin to the present day. In 50 years it might have a different name. Settlers could obviously take advantage of a pre-existing earthwork when choosing a location, if one existed. I'm not asserting that the ditch is older, I just prefer justified uncertainty to unjustified certainty. There may be a bureaucratic reason to claim knowledge here, for the purposes of protecting the ditch, that I'm unaware of. I'm also informed by DonJaime that "Mykelldiche" is Middle English rather than Anglo Saxon anyway, which tends to support my point - although they did write "in origin".
Some people guess that the Romans built the ditch, it crosses three ancient Roman roads and would have helped to control access to the area, the camp and the vicus. Roman Manchester wasn't a huge camp, usually manned by around 500 auxiliaries, but equipped to house and supply legions in transit to Scotland, south, or east to York. Manchester was a very strategically significant point on the map of Roman Britain, rich countryside, plenty of river access, ringed with hills, and on the major North-South route. Roman military engineers would certainly not have shied away from this challenge, especially given the need to control the local Celts, thought to be the Setantii tribe of the Brigantes federation.
I grew up in Burnage, very close to a section of the ditch that has a cycle/running path called the "Fallowfield Loop" and I have walked and cycled and ran along it many times, probably clocking up hundreds of miles throughout my life. In the summer the berry briars, saplings and bushes erupt into a strip of urban forest. In the winter, sometimes in the summer too, the ditch will flood, and one wide section becomes a small wetland. I know this route intimately, but I never knew it had a name until about 5 years ago when I started researching a novel that is set in Manchester.
The Nico Ditch, or Nico's Ditch
We don't know the ditch's age or its original purpose, but we do know its proper name today. Some people say that "Nico" is simply a corruption of "Mykkel". This ignores a parallel etymology derived from the strong folk tradition that Manchester has long been home to dangerous creatures who take the lives of the people who live there. This tradition is codified in place names like "Boggart Hole Clough", which can be transliterated as "Valley of the Monster-Hole" - "Boggart" here is cognate with boogeyman. There are a multitude of stories centred on the landscape and people of Manchester being stalked by demons and monsters throughout the centuries. One particularly vivid example is the "Hnickar", an Anglo Saxon term for a water-demon that would trap and drown, kill and eat, those who pass unsuspecting. Obviously names and words become corrupted and change their sound over time. Nowadays we have "the Pusher" in Manchester.
Imagine my surprise 5 years ago, as I began to write my own story of the creature that has stalked this land for thousands of years, when I learned that the ditch I had passed beside so often was named after the Hnickar, garbled to "Nico", who became my monster.