The royal centre of Forteviot in Strathearn, Perthshire is one of the most famous early medieval sites in Scotland. It has traditionally been regarded as a royal capital, first of the powerful Pictish kingdom of Fortriu and then of the early Scots. But the royal centre is poorly understood. Much of it disappeared in the early 19th century, swept away by the Water of May, leaving only fragmentary sculpture. However, the function, date, and iconography of the magnificent arch, discovered in the river bed in 1836, have until now remained obscure. This first full-scale study of this famous site sheds new light on Pictish kingship and the Church, enabling one of the most powerful Pictish kings, Unuist son of Uurguist, to emerge from the shadows of historical obscurity.