That strip of rounded glacial hills which runs right across the country from Strangford Lough in County Down to Clew Bay in Mayo.

A drumlin (Irish droimnín, a little hill ridge) is an long whale-shaped hill formed by glacial action.  Drumlins may be more than 45 m high and more than 0.8 km long, and are often in drumlin fields of similarly shaped and sized hills.