Among the following sentences:
Schön ist es hier.
Es ist schön hier.
Hier ist es schön.
Es ist hier schön.
I am wondering what are the differences among them. Could anyone help?
The difference is not in meaning, but in emphasis.
Schön ist es hier = "Wow, nice place!"
This emphasizes the pleasantness of the place as opposed to other qualities, such as expensiveness of a restaurant (which might well go along with niceness).
Es ist schön hier = "This is a nice place."
This emphasizes the niceness as well, but not as forcefully.
Hier ist es schön = "This is a nice place."
Emphasizes the place rather than the quality. You might say that after you've tried another, perhaps less nice place.
Es ist hier schön = "The place is nice."
This emphasizes nothing in particular, and in fact is least likely to be said; it sounds more like a textbook definition than part of normal conversation.