Tacna, officially known as San Pedro de Tacna, is a city in southern Peru and the regional capital of the Tacna Region. A very commercially ac…Tacna, officially known as San Pedro de Tacna, is a city in southern Peru and the regional capital of the Tacna Region. A very commercially active city, it is located only 35 km north of the border with Arica y Parinacota Region from Chile, inland from the Pacific Ocean and in the valley of the Caplina River. It is Peru's tenth most populous city.