One of the engineering feats of the 5th century, Sigiriya Rock Fortress is made up of the ruins of what was once the palace of Kashyapa I, the king who seized the throne after he murdered his father. There's a tragic story behind the fortress which was built so it would be impenetrable, and it was until it fell to ruin. Make sure you learn some history of Sigiriya before you visit so you have a better understanding of what it is you are seeing.