During his second journey, while at Troas, Paul saw a vision of a man of Macedonia. Luke gives the following record of the vision and of the subsequent action of the apostle.
A vision appeared to Paul in the night: a man of Macedonia was standing and appealing to him, and saying, “Come over to Macedonia and help us.” When he had seen the vision, immediately we sought to go into Macedonia, concluding that God had called us to preach the gospel to them. (Acts 16:9-10)
Paul and his companions, including Luke, landed at Neapolis (modern Kavalla). The text indicates that the real goal of their mission was to reach the Roman colony of Philippi. Philippi was about 10 miles away, and could be reached by traveling the famous Via Egnatia across Mount Symbolum. Neapolis had been founded in the 7th century B.C. and served as the port of Philippi. Here is a photo of the modern port at Kavalla in northern Greece.
Luke uses his words sparingly.
So putting out to sea from Troas, we ran a straight course to Samothrace, and on the day following to Neapolis. (Act 16:11)
Paul and his companions sailed from Philippi (the port of Neapolis) to Troas on the return from the third journey (Acts 20:3-6.