The name Ariel is a poetic name for Jerusalem. The prophet Isaiah used the name in a "woe" oracle warning people to turn from their wrongdoing (Isaiah 29:1–2, 7).
In the oracle, Isaiah called Jerusalem "Ariel" (which means "hearth of God"). Naming one part of a whole thing for dramatic effect is a poetic device called a "synecdoche." Jerusalem is the location of the altar of burnt offering, but Isaiah refers to the entire city as an altar.
In a dramatic play on words, Isaiah pronounced a judgment of God on Jerusalem. The city of the hearth of God would face destruction from enemies and become an ariel, a pagan altar hearth.