Enclosed behind Dublin Castle, the Dubh Linn garden looks like a formal piece of landscaping styled with a touch of Celtic nationalism. The central lawn is circular, with smaller gardens in the corners, and it’s accessed from either an open stretch in front of the Chester Beatty Library or through a pedestrian-scaled gate in the wall opposite the State Apartments. It’s a nice place to sit, particularly on a sunny day, and the widely-spaced benches mean it’s well suited to a private conversation.

The name Dublin is derived from the Irish name Dubh Linn (meaning "black pool"). The common name for the city in modern Irish is Baile Átha Cliath (meaning "town of the hurdled ford"). Áth Cliath is a place-name referring to a fording point of the Liffey in the vicinity of Heuston Station. Baile Átha Cliath was an early Christian monastery which is believed to have been situated in the area of Aungier Street currently occupied by Whitefriar Street Carmelite Church.
 
The subsequent Scandinavian settlement was on the River Poddle, a tributary of the Liffey, to the East of Christchurch, in an area now known as Wood Quay. The Dubh Linn was a lake used by the Scandinavians to moor their ships and was connected to the Liffey by the Poddle. The Dubh Linn and Poddle were covered during the early 1700s, and as the city expanded they were largely forgotten about.
 
The Dubh Linn was situated where the Castle Garden is now located, opposite the Chester Beatty Library in Dublin Castle.