Walls Castle is the odd name for a Roman bath house, and the building still stands to a height of about four metres, one of the tallest Roman structures in northern England. It stood outside the fort of Glannoventa at Ravenglass, a harbour station at the meeting of three rivers, the Irt, the Mite and the Esk, and in the dry shelter of the dunes it has survived because its walls were thick and well built. You can walk around it on a short path from the village, and see niches and a doorway in the thick walls. The fort itself lies mostly under farmland and the railway.
Ravenglass is a tiny place, a single street of cottages facing the estuary, where the tide goes out a long way and the light is silvery. The narrow-gauge railway to Eskdale, known as La'al Ratty, starts here and chugs seven miles up the valley, carrying walkers and families behind a small steam engine. Muncaster Castle stands on a ridge above the estuary, with rhododendron gardens and a reputation for ghosts. The Lake District National Park is a few kilometres inland, and the sea is on the other side.
The best road for a rider runs up Eskdale. It follows the river through oak woods and sheep fields to Boot, then climbs to the Hardknott Pass, a narrow, steep and exciting road with hairpin bends and gradients of up to 30 per cent in places. At the top stand the ruins of Hardknott Roman fort, a high stone enclosure with a wide view across the mountains to the sea. The pass is only for the confident, and snow, ice or fog can close it altogether in winter. Wrynose Pass follows on the far side and is nearly as hard. Go in dry weather, and take your time.
Seascale, seven kilometres up the coast, has a small shop, and the nearest town of any size is Egremont, sixteen kilometres away, or Whitehaven further north. Fill up before you head for the passes, and bring water. The station tea room serves tea and cake, and the pub by the estuary does a decent lunch. Bring a jacket, because the wind off the sea is cold even in July.