At the top of the hill of Frourion, considered the citadel of ancient Larissa, south of the Ottoman Bezesteni, the remains of a large basilica were discovered and unearthed in 1978.
The prominent position of the basilica, the inscription "Of Achilles Archbishop this is the work," found in the fragments of a well’s mouthpiece and the inscription “ACHILLION” stamped on various large blocks of stone led to the identification of the basilica as the church dedicated to the patron saint and first bishop of the city, St. Achilles.