León has been a city for nearly two thousand years, since a Roman legion made camp here, and the old rectangle of the Roman walls is still partly visible in the heart of the town. The name itself comes from the legion, not from the lion that now sits on the city's flag, though locals prefer the lion. In the Middle Ages León was the capital of a kingdom, and later it became a major stop on the pilgrim road to Santiago, so the old quarter is full of churches, monasteries and inns that pilgrims used for rest.
The three things to see are the cathedral, the Basilica of San Isidoro and the Hostal de San Marcos. The cathedral is Gothic, light and slender, and its walls are almost entirely made of stained glass, so that on a sunny morning the interior glows red and blue. San Isidoro, nearby, holds a royal burial chamber with twelfth-century wall paintings that are some of the best Romanesque frescoes in Europe. The Hostal de San Marcos, a sixteenth-century former convent, is now a luxurious hotel, with an elaborately carved front facing the river. Even Gaudí left a mark, with a neo-Gothic building called the Casa Botines on the main square.
At the end of a long ride south to north across the meseta, León makes a very good finish. With over a hundred thousand people, it has plenty of fuel, bike-friendly parking on the edge of the old town and hotels for every budget. In the evening the narrow streets of the Barrio Húmedo fill with people going from bar to bar, and in the traditional way each drink comes with a free small plate of food, so it is possible to dine well without ever sitting down. The cured meats, especially the local cecina, a smoked beef, deserve a try, and so do the blood sausages.
To the north of the city the Cantabrian Mountains rise, and the roads there are among the best in northern Spain, with passes and gorges, but that is for another day. Today you roll in off the plateau, find a place to park, and walk. Spring and autumn are best, because winter nights can be bitterly cold and summer afternoons are hot.