Where did Paul intend to go after Mysia, and what stopped him?

Les explains that Paul had been ministering in western Turkey, then Asia Minor, and had gone up to Choas from the area of Derbe and Lystra. He had intended to go back to northern Turkey through the area around the Black Sea and then to Asia. Scripture says they were forbidden by the Holy Spirit to preach the Word in Asia. After they came to Mysia, they intended to go into Bithynia, which lies along the Black Sea, and that was evidently Paul's intended route, and then probably back to Antioch in Syria. But the Holy Spirit permitted them not. Passing by Mysia, they came down to Choas, where Paul was expecting to meet Titus. Then a vision appeared to Paul in the night, and a man of Macedonia beseeched him to come over into Macedonia and help.