Clusters of five or more prehistoric round barrows, typically including bowl barrows and a range of fancy barrows. The spacing and number of barrows varies considerably, but some of the largest such cemeteries are those around Stonehenge in England and can include more than 30 separate barrows spread over an area more than 300 m across. Such cemeteries are said to be linear when there is a marked axis to the spread of barrows; nuclear when the barrows form a tight cluster; or dispersed when the individual barrows are spread out and lacking any obvious pattern to their arrangement. In many cases a round barrow cemetery develops around what Leslie Grinsell called a ‘founder's barrow’, usually a particularly large barrow or a Neolithic barrow that provides a focus for later activity. Few barrow cemeteries have been excavated, but where investigations have taken place there is usually abundant evidence for flat graves between and around the barrows. Such groups of burials accumulate over long periods of time, typically many centuries.