Carlisle has been a frontier city for nearly two thousand years, and the vallum that runs across its northern edge is part of the reason. North of the River Eden, in the suburb of Stanwix, stood the largest fort on the whole of Hadrian's Wall, home to a cavalry regiment a thousand strong. The fort lies under the streets and the churchyard now, but the line of the Wall and its rear earthwork, the vallum, can be traced across the fields and gardens to the west, and walkers on the national trail follow it out of the city towards the Solway.
The vallum is one of the odder features of the frontier: a broad, flat-bottomed ditch with a mound on either side, running south of the Wall for most of its length. Archaeologists still argue about its exact purpose, but it seems to have marked a military zone, controlling who could approach the Wall from the south. In this stretch it survives as a faint hollow or a change in the field boundaries, easy to miss unless you know what you are looking for.
Carlisle itself is full of history. The castle, built of red sandstone, has been besieged more times than almost any other in England, including during the Jacobite rising of 1745, when Bonnie Prince Charlie's army took the city before retreating. The cathedral, also red sandstone, is one of the smallest in England. The Tullie House museum is excellent on the Roman period and on the Border Reivers, the raiding families who made life in this region violent for centuries.
Riding around Carlisle is a matter of city roads, roundabouts and the M6. The A7 north towards Longtown and the Scottish border, and the A595 west towards the coast, are quick routes out. Within the city, watch for cyclists, buses and speed cameras. Once you clear the suburbs, the roads into the countryside are quieter and more pleasant, with gentle bends and views of the fells.
Carlisle has every service you could want: fuel, supermarkets, cafés, pubs and restaurants. The old town around the cathedral and the market cross has plenty of places to stop for a coffee or a meal. The weather is famously changeable, so be prepared for rain. Walk along the river and over the bridge to Stanwix, and you will be following in the footsteps of Roman cavalrymen.