River Main flows through the heart of quintessential medieval Germany and while less well-known than the Danube or Rhine, it’s a major tributary of the latter. It weaves a glorious 530 km (330 miles) route from the lush valleys of the German Highlands to romantic Bavaria, passing some of the most picturesque medieval towns in the country before it reaches historic Mainz.The Main’s only navigable section is between Mainz and Bamberg.