Third largest river after River Slaney and River Barrow which flows through the County of Carlow is River Burren.
Length of the river Burren is 39 kilometres (24 miles).
The River Burren flows through the Carlow town.
Burren River has its source located on the north face of Mount Leinster. Then it flows northward under the R724 (Ullard Bridge, west of Fenagh) and under the N80. It continues northward through Rathoe meeting the Aghalona River in Inchisland and turns westwards, passing under the M9 in Moyle Big. The Burren River goes under the N80 again at Ballinacarrig Bridge. It flows through the southern part of Carlow town and passes under the railway line, R448 and R417 (Burrin Street) and then drains into the River Barrow.
The River Burren is renowned as angling river. Fish species include brown trout, three-spined stickleback, nine-spined stickleback, Atlantic salmon, stone loach, common bream, roach, perch and lamprey. Especialy Burren River is considered to be a very good brown trout fishery.
Also Grey Herons are often seen on the riverside of Burren River, standing motionless in or near water waiting to strike at their prey.