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
The word that most likely fits the question presented would be "sacred", as the definition of "sacred" is being connected with God (or the gods) or dedicated to a religious purpose.
• "That burial site is considered SACRED".