Last but most certainly not least, we have Chillon Castle. While today, it does not function as a prison, it did function as one in the 16th century Wars of Religion. Nowadays, it’s a tourist attraction and is home to many forms of interior architecture, more specifically 14th century medieval murals, amongst many others. The exterior sits on a piece of land surrounded by water, and with the mountains behind it, it’s certainly one of the most beautiful prisons ever made. It is located on Lake Geneva in Switzerland, and is now known as a historic monument in Switzerland.