In the high, narrow Val Mustair, at the point where Switzerland meets South Tyrol and the Stelvio national park, there is a Benedictine convent that was founded, according to tradition, by Charlemagne himself around the year 800. Whether or not the emperor's role is exactly as the legend has it, the convent of St John is certainly Carolingian, and it keeps the largest cycle of Carolingian wall paintings anywhere. The figures, painted in the early ninth century, cover the walls of the church in red, yellow and green, in a lively, slightly naive style, with scenes from the life of David and the story of Christ, and later Romanesque frescoes were painted over them in places. UNESCO listed it in 1983.
The convent is still home to a community of Benedictine nuns, and the church is open to visitors, with a museum in the old tower that explains the history and the restoration work. It is a modest, quiet place with white walls, grey roofs and the mountains standing behind it. The valley's language is Romansh, a descendant of Latin that is spoken by only a few tens of thousands of people, and you will see it on signs and hear it in the shops. A slice of Engadine nut cake in the village is the proper reward.
This is outstanding riding country. The Ofen pass, at 2,149 metres, climbs from the valley through the Swiss National Park to Zernez, with long, flowing bends and larch forest, and the Umbrail pass, at 2,501 metres, is the highest paved road in Switzerland, joining the Stelvio road above Bormio. The Stelvio itself, at 2,757 metres, with its dozens of hairpins, is just across the border, but all of these passes are closed by snow from late autumn until late spring, so check before you go. Summer weekends are very busy.
Tubre, across the border in Italy, and Mustair itself are small, and fuel is better bought in Mals, a larger town in South Tyrol a short ride away, and in the valley's main villages. Prices are lower on the Italian side. Bring warm clothes, because the passes are cold even in July, and carry some cash in both euros and francs.