Carlisle's city walls are fragmentary but real — substantial sections of the medieval defences survive, and you can walk along them and through the remaining gateways to get a sense of how thoroughly fortified this city once was. The best-preserved stretch runs along the north and west sides of the city, near the castle. The three medieval gates — Scotch Gate, English Gate, and Irish Gate — have all been demolished, but the line of the walls survives.
The walls date from the 12th century in their earliest surviving form, though they were rebuilt and strengthened repeatedly through the centuries of border conflict. Standing on the remains and looking out over the Eden valley to the north, it is easy to see why controlling Carlisle mattered so much: this was the only good route between England and Scotland on the western side of the country.