The Castle Tunnel is a two-lane tunnel that connects Union Drive East with Union Drive West via a tunnel under Castle Gardens at the southern tip of Algonquin. It passes under the pedestrianised area of Castle Gardens and was presumably built to bypass the busy financial district, The Exchange.
Intersections
| Location | Type | Road | Direction |
|---|---|---|---|
| The Exchange | 
|
Union Drive West | n/b direction: Exit toward Union Drive West s/b direction: Entrance from Union Drive West |
| Castle Gardens | 
|
Union Drive East | n/b direction: Entrance from Union Drive East s/b direction: Exit from Union Drive East |
Trivia
- It is based on the Brooklyn-Battery Tunnel, although it doesn't connect to Broker, and the Battery Park portion of the FDR Drive in New York.