What's the point of adding とした here in this sentence?


Here is the sentence of my question.

希望に満ち溢れていたはずの"あなた"がなぜあんなに荒凉とした場所にうずくまっていたの。

I can understand what it's trying to say to some degree yet it confuses me why
とした is used in the sentence.

With the wonder I checked とした up in the dictionary and got no explanatory
answer. And I wonder if it's an adjective or a particle added to modify nouns
and turn them into adjectives.

