Simplify the following text for a Grade 4 native English-speaking person.
Original: Bithynia was an ancient region , kingdom and Roman province in the northwest of Asia Minor , adjoining the Propontis , the Thracian Bosporus and the Euxine ( today Black Sea ) .
Simplified: Bithynia was an old kingdom of a Roman province in the northwest of Asia Minor . It was at the coast of the Black Sea .