Complex sentence: It is mainly known for the ruined Godstow Abbey (also known as Godstow Nunnery), which was given to the foundress by John of St John around 1133 and was expanded in 1139 through an additional grant of land.
Split into simpler sentences: It is mainly know for the ruined Godstow Abbey (also know as Godstow Nunnery). It was given to the foundress by John of St John around 1133 and was expanded in 1139 through an additional grant of land.