Cueva literally translates to "cave". While it's a simple word, Cazzu uses it as a powerful metaphor for a dark, isolated place of emotional brokenness.
She sings, "Te encontré en la cueva" (I found you in the cave), to describe finding someone at their lowest point. The song's story revolves around this idea, predicting the person will return to this metaphorical cave, as they are their own "propio prisionero" (own prisoner).
In "LA CUEVA," Cazzu tells a story about rescuing someone from a dark place, only to be let down. She found this person in a metaphorical "cueva" (cave), describing them as "totalmente roto / totalmente oscuro / totalmente loco" (totally broken / totally dark / totally crazy). She says she "lamí tus heridas / y encendí tu sol" (licked your wounds / and lit your sun), helping them heal and showing them a better life. But the gratitude never came. Instead, he "solamente pensaste en vos" (only thought of yourself).
Now, she's looking to the future and asking him some tough questions. What will he do when he's alone and can't use someone else to distract himself from his sadness? She predicts that while she will eventually "florezca" (blossom) and move on, he is doomed to return to his cave. Even if he could buy the whole world, he is "tu propio prisionero" (your own prisoner). The final message is absolute: for him, a return to her is impossible. "Y volver, volver, volver / no se va a poder" (And to come back, come back, come back / it won't be possible).