From Grand Theft Wiki

Emerald
Liberty City Subway station
Station information
Line	A/J Algonquin Outer Line
Service	A/J
Platforms	2
Tracks	2
Other
Borough	Algonquin
Next north	Easton: A/J
Next south	Castle Gardens: A/J

Emerald is a station on the Liberty City Subway system in Grand Theft Auto IV. It is located on Emerald Street, between Luddite Row and Albany Avenue. The station serves the neighborhood of Chinatown in Algonquin. The A/J Algonquin Outer Line stops at the station.