The Thames and Severn Canal passes along the edge of Cotswold Water Park. It was completed in 1798 and was planned as part of a canal route from Bristol to London. At its eastern end it connects to the River Thames at Inglesham Lock near Lechlade, while at its western end it connects to the Stroudwater Navigation at Wallbridge. Since 1972 the Cotswold Canals Trust has been working to restore the canal and the Stroudwater Navigation so that there can again be a navigable link between the River Thames and the River Severn.
A walk along the section of Canal that passes along the edge of Cotswold Water Park will bring you past Cerney Wick Roundhouse. It is one of five distinctive buildings that were built for use by lock-keepers and lengthmen. The roundhouses have 3 floors, the lower floor would have been a store, while the first floor provided a living area and the second floor a circular bedroom. The roundhouse at Cerney Wick is now privately owned.
A 5 mile circular walk starting at South Cerney takes you past the Roundhouse along the disued Canal and the old railway line. For more details http://www.theaa.com/walks/around-the-lakes-of-the-cotswold-water-park-420502
Visitors walking around the Lower Mill Estate will find another roundhouse in Mill Village, the oldest part of the estate.