[2][3][4] The Vartry rises in Calary Bog under the Great Sugar Loaf mountain in northern County Wicklow.

Passing through a Dublin municipal reservoir complex, it flows east towards Ashford under Annagolan Bridge, and down through Devil's Glen.

From there it passes the Nun's Cross Bridge (dating from the 18th century) on through Ashford, under the N11 road and continues eastwards into Broad Lough, which flows towards Wicklow town.

This lake and surrounding wetlands evolved when a sand spit formed along the coastline[5] cutting off the Vartry from its original egress.

This sand spit is called The Murrough/Murragh and it carries the Dublin to Wicklow coastal railway line built in the 1860s.