An Oxford College wall in dis-repair.

Whilst the majority of Oxford has been built in limestone, throughout its history the source of the limestone has constantly changed. The ‘Headington stone’ is the closest quarry and has provided the majority of the stone for the iconic colleges. This ‘oolitic limestone’ is easily damaged by acid rain and soot from cars. This has meant most buildings in Oxford have had to replace their walls at some stage during their lifetime.