Overnight we have cruised upstream to Esztergom, one of Hungary’s oldest towns, a royal capital during medieval times and today the seat of the country’s archbishop. We have a guided tour of the famous neoclassical basilica, standing sentinel over the Danube on the border with Slovakia, and boasting one of the world’s largest altarpieces and a wealth of priceless religious artefacts. The castle is also worth exploring; it was the seat of government until the Ottomans invaded in the 16th century. Nestling below are myriad atmospheric churches resonating with the enchanting sounds of choir; this is the best of provincial Hungary and is little changed since Habsburg times.