in the room
of the people
by the river
from the teacher
for the party
The object of a preposition can have its own modifiers, which also are part of the prepositional phrase.
in the smoky, crowded room
of the remaining few people
by the rushing river
from the tired and frustrated teacher
for the midnight victory party
Prepositional phrases function as either adjectives or adverbs.
The woman in the trench coat pulled out her cell phone.
The prepositional phrase in the trench coat acts as an adjective describing the noun woman.
Most of the audience dozed during the tedious performance.
The prepositional phrase during the tedious performance acts as an adverb modifying the verb dozed.