Tainan High-Speed Railway Station 高鐵臺南站 is the city's most modern entrance point. Located around 15km south from Tainan Railway Station, it's not too far from the city's downtown. Nowadays there is a direct railway connection through the Shalun Line, see a map here. But for your convenience, there are cabs and free shuttle buses right outside the station. My wife and I took one and we needed about 30 mins to reach central Tainan. The bus stops at several stops, which was very convenient for us, because it stopped in the area near our hotel.
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