hi'Leyi'a was a vast underwater city located on the planet Pacifica.

In 2379, Melora Pazlar was frustrated that no one could understand that she was no more out of place in a normal gravity environment, than a Human would be in the city of hi'Leyi'a. (TTN novel: Taking Wing)

Doctor Beverly Crusher, Commander Miranda Kadohata, and attorney Paul Dillingham visited hi'Leyi'a for the first time in 2381, for a meeting with Secretary of Interplanetary Affairs Osseo Bemidji. (TNG novel: Losing the Peace)