Behind the Mazu Temple, the fort was a stronghold of Dutch power until its 1661 capture by Koxinga after a nine-month battle. Most of it has been reconstructed, but it's still an impressive site. A small museum on the grounds highlights the history of the Dutch occupation of Taiwan. Buses come from Tainan train station; the stations you want are respectively Post Office (郵局) and Anping Fort (安平古堡).