Built over the 8th century onwards and reworked extensively in the late medieval period, Ascoli's cathedral of Sant'Emidio sits on the east side of Piazza Arringo and remains the city's principal church. The travertine façade is Renaissance; the interior preserves the original Romanesque cross plan with substantial 15th-century rebuilding.
The Crivelli polyptych — a luminous, gilded, multi-panel altarpiece of the Virgin and saints — is the major draw and is in the south-west chapel as originally intended. The crypt, partly carved into the rock, holds the relics of Sant'Emidio (the city's patron) and is open to visitors. Free entry, modest opening hours; check before visiting.