Complex sentence: The cursus is the oldest and largest ancient monument at Thornborough, it is almost a mile in extend and runs from Thornborough Village, under the (later) central henge and terminates close to the River Ure in a broadly east/west alignment.
Split into simpler sentences: The cursus is the oldest and largest ancient monument at Thornborough. It is almost a mile in extend and runs from Thornborough Village, under the (later) central henge and terminates close to the River Ure in a broadly east/west alignment.