A St. Nicholas Cathedral has stood in the Old Town since the 13th century. If you're saying this looks too new to be that old (especially if you know architectural styles), you're right. It was partially destroyed by the French when they invaded in the 17th century. So in the 18th century the church was torn down and reconstructed. A beautiful baroque church took it's place.

Prague is such a fascinating town because it avoided the brunt of two World Wars, but that doesn't mean it remained unscathed throughout it's history.