The Thames is a beautiful river. It flows through London
Combining these two sentences with relative pronoun:
(1) The Thames is a beautiful river, which flows through London.
or
(2) The Thames, which flows through London, is a beautiful river.
or
(3) The Thames, which is a beautiful river, flows through London.
Are the three options above (1), (2) and (3) both grammatically correct? If this is the case, which one sounds more natural than the other?
Your help is precious. Thanks in advance.