Hello how may I help you? Yes, I would like to know more about Prague. Okay, one moment please. thx The largest castle in the world is located in Prague. Cool, what river runs through it? The Vlatava river runs through it. Cool. What else? It has been preserved for the last 100,000 years. Anything else I can help you with? Wow. That is before civilization started, so cool I am good. Okay, Have a wonderful day!