Answer :

An adjective is a descriptive word

In this sentence, "natural" is the adjective.
Wonder is used as a noun, so even though it is a descriptive word, it is used like it is an object, so IN THIS SENTENCE it is not an adjective.
"Grand" in "Grand Canyon" is part of the title, and is also not considered an adjective

Answer:

- Natural.

Explanation:

Adjectives are defined as the words that qualify or modifies noun or pronoun. The adjectives function to modify a noun or pronoun by offering more details about it that may include various aspects like size, color, quality, number, etc.

As per the question, the adjective employed in the given statement is 'natural' that qualifies/modifies the noun 'wonders'. It could have been 'grand' but 'The Grand Canyon' here together works as a proper noun in the sentence. Thus, 'natural' is the adjective in the sentence.