Cirencester is a market town in Gloucestershire, England, 80 miles (130 km) west of London. Cirencester lies on the River Churn, a tributary of the River Thames, and is the largest town in the Cotswolds. It is the home of the Royal Agricultural University, the oldest agricultural college in the English-speaking world, founded in 1840. The town's Corinium Museum has an extensive Roman collection. The Roman name for the town was Corinium, which is thought to have been associated with the ancient British tribe of the Dobunni, having the same root word as the River Churn. The earliest known reference to the town was by Ptolemy in AD 150.