What does Jeremiah 22:6 mean?

This is what the Lord says about the palace of Judah's king: 'To me, you're as beautiful as Gilead, as majestic as Lebanon's forests. But I swear I'll turn you into a desert, a city with no one living in it.' Jeremiah 22:6 - Modern Text Bible

(God compares the palace to beautiful places, but says he'll make it empty and desolate if the people don't change.)