From this page above, I found some examples showing prepositional phrases as subjects, but the predicate nouns are all singular like the ones below. So their verbs are, of course, singular.
1) On a boat is where I want to be.
2) Beyond the backyard is marshland.
3) Under the couch is an abyss where toys are lost.
When we use prepositional phrases as subjects, is there the subject-verb agreement rule to follow?
If the predicate nouns are plural, which verb form should I use? Singular form or Plural form?
1) Behind me is/are cute puppies.
2) Behind the man stands/stand two tall buildings.
What if there are two prepositional phrases functioning as the subject?
3) Before me and under the sky is/are a scenic view.