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?