Jax-Ur: Look at it this way, Kal-El: Death is better then the Phantom Zone.
Superman: I'll take your word for it.
Jax-Ur: So this is Kal-El, son of Jor-El. Your father was a clever man, though I see you share his poor judgment in choosing sides.
Superman: Glad to disappoint you.
Professor Hamilton: If anyone deserves their own "Fortress of Solitude", it's you.
Superman: Fortess of Solitude?
Lois: I'm gonna personally lead the army that vaporizes you two.
Mala: Or vice-versa. Either way, see you soon.
Lois: It must hurt your fingers, clamping down on my throat like that...
Mala: I'll live.
In this series, it is Professor Hamilton who coins the phrase "Fortress of Solitude".
The key to the Phantom Zone projector, according to Professor Hamilton, is a crystal that matches the correct vibrational frequency. This is similar to how the Flash (in the comics) can travel between dimensions by altering his internal vibrations.