The cathedral at Old Sarum was probably started under Bishop Hermann (d. 1078), when the see was moved from Sherborne (in 1075); much of the work was conducted by his successor Bishop Osmund (d. 1099). This structure was placed inside the outer walls of the castle (that follow the line of the Iron Age hillfort), and completed in 1092.
The cathedral was rebuilt by Bishop Roger (d. 1139) and expanded by Bishop Jocelin de Bohun (d. 1184). The foundations of the new Salisbury cathedral were laid in 1220 under Bishop Richard Poore (1217-28), and the remains of the first three bishops of Salisbury were moved from Old Sarum in June 1226. The old cathedral was then dismantled and the stone reused for the new building.