We will take a trip across the country on a train . Adverb phrase?

An adverb phrase modifies a verb, adjective, or other adverb, providing additional information about how, when, where, or to what extent something is done. In the sentence "We will take a trip across the country on a train," the phrase "across the country" acts as an adverbial phrase, indicating the location of the trip. It describes where the trip will take place.