The town lies at the confluence of the River Liffey and the River Griffeen, its tributary. The picturesque old town retains its character, despite hosting ever-expanding areas of new housing that are essentially overspill developments for nearby Dublin. These new areas lead east from the town towards the Liffey Valley Shopping Centre and southeast towards Clondalkin. As part of Transport 21, a further major expansion south of the Dublin-Cork train line is planned on the lands of Adamstown.