Rotunda sv. Martina

The Rotunda of Saint Martin stands out for its squat, circular stone walls and the single, dark iron cannonball embedded directly into its masonry. Built in the eleventh century, it remains the oldest surviving Romanesque building in Prague. While the rest of the Vysehrad fortress underwent massive gothic and baroque reconstruction, this tiny chapel stayed largely unchanged. During the nineteenth century, the city used it as a gunpowder store, and the cannonball serves as a reminder of the Swedish siege in sixteen forty-eight.