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The sentence should read as follows: It includes a delightful public square with centuries-old magnolia trees.
Here is the reasoning for the changes we have made: (1) We can deduce from the word "includes" that this sentence is in the present, meaning we will use present tense for all of the adjectives. The word "delighted" in the original sentence is in past tense and therefore needed changed. (2) We had to change the word "century-old" because of the word "trees" at the end of the sentence. As the sentence originally was, you would have to say that there was "a delightful public square with a century-old magnolia tree", but if you simply change the word "century-old" to "centuries-old" it fits right into the sentence that we have already established.
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