Esztergom, poised at a bend in the Danube that forms the border between Hungary and Slovakia, is a must-do stop on any Danube River cruise. The city was the capital of Hungary from the 10th until the mid-13th century when the king moved the royal seat 29 miles upriver to Buda, a hill town across the river from Pest. Esztergom, however, remains the seat of the Primate of the Roman Catholic Church in Hungary, and its massive basilica is the largest in the country. The site on which the basilica sits is a glorious vantage point that looks down the Danube and over the bridge to Slovakia.