Is there no subject in a sentence like "Under the tree is a dog"?

I was trying to find out sentences without a subject, only object, and I came across
this

where the poster gives following sentences as an example

Under the tree is a dog.
Next to the park stands a clock tower.
Underneath his jacket was his white tucked in t-shirt and jeans.
Deep beneath the sea lies the mysterious kingdom of Captain Nemo.

Aren't the subjects in them: "the tree", "the park", "jacket", and "the sea" respectively?

Answer

These are all examples of locative inversion, where the subject and the prepositional phrase shift their normal positions. Usually the subject is at the beginning of the sentence, but not in these examples.

if you want to look into the topic of sentences without subjects, see the classic paper Quang (1971) on English imperatives.