Thessaloniki's walls are the great monument that holds the whole city together. They run in a long triangle from the sea up the hill and back down, and in places they stand ten metres high, with square and round towers, brick bands and later repairs patched in like scars. The first walls were built in the late fourth century and again in the fifth, when the city was a vital Roman port on the Via Egnatia, the road that linked the Adriatic with Constantinople. Later emperors repaired them over and over, and the Ottomans too, and the pattern of stone, brick and rubble tells the story to anyone who looks closely.
At the top of the hill stands the Eptapyrgion, the Fortress of Seven Towers, which the Ottomans used as a prison and which held prisoners until 1989. The Trigonion Tower, a three-sided bastion at the corner, is the most famous point, and from its platform you look over the whole city. The south walls, along the harbour, were pulled down in the nineteenth century to let the city grow, so the sea front is open now. Today a walk along the surviving sections offers fine views and an atmosphere of wild flowers and broken stone.
For a rider, the road that follows the line of the walls is the best bit of tarmac in town. It climbs from the lower suburbs through the old quarter, with twisting streets and hairpin bends that feel almost Alpine in miniature, and the best views of the gulf. Some lanes are very narrow and steep, so a small bike is better than a tourer. After rain the cobbles are treacherous. Go early on a clear morning, or an hour before sunset, to enjoy light and fewer cars.
Ágios Pávlos is the nearest district and has fuel and shops on its main roads, with the larger Sykiés beyond. Take water with you, and wear a hat in summer, because the walls offer little shade. The tavernas near the Trigonion serve grilled meat and salads, and the owners are used to walkers and cyclists. There is a legend that the city was saved from attack by a vision of Saint Demetrios on the walls, which gives you something to think about as you stand on the stones at dusk and watch the lights come on below.