Many of Europe's grandest and most picturesque castles are sited near some of the best-known rivers on the continent. Built to protect waterfront communities, the fortifications also served to guard the approach to towns and villages against attack, and would have provided a formidable deterrent to any potential enemy. Most of these castles date back to the Middle Ages, and have survived to welcome today's tourists. But even in glorious ruin, these ancient fortresses still exude a romantic and beguiling atmosphere.
So, where can you admire these exceptional strongholds, and what rivers are they standing on? Click through and take to the water to find out.