St Rule's tower is located in the Cathedral grounds but predates it, having served as the church of the priory up to the early 12th century. The building was retained to allow worship to continue uninterrupted during the building of its much larger successor. Originally, the tower and adjoining choir were part of the church built in the 11th century to house the relics of St Andrew. The nave, with twin western turrets, and the apse of the church no longer stand. The church's original appearance is illustrated in stylised form on some of the early seals of the Cathedral Priory. Legend credits St Rule (also known as St Regulus) with bringing relics of St Andrew to the area from their original location at Patras in Greece. Today the tower commands an admirable view of the town, harbour, sea, and surrounding countryside. Beautifully built in grey sandstone ashlar, and (for its date) immensely tall, it is a land- and sea-mark seen from many miles away, its prominence doubtless meant to guide pilgrims to the place of the Apostle's relics. In the Middle Ages a spire atop the tower made it even more prominent. The tower was originally ascended using ladders between wooden floors, but a stone spiral staircase was inserted in the 18th century.