Complex sentence: It is the most extensively explored of all the Northumbrian monasteries of the 7th and 8th centuries, beginning in 1833 when workmen building houses on the headland found human burials and Anglo-Saxon artefacts.
Split into simpler sentences: It is the most extensively explored of all the Northumbrian monasteries of the 7th and 8th centuries. The first excavation began in 1833 when workmen building houses on the headland found human burials and Anglo-Saxon artefacts.