Duomo San Flaviano, Renaissance cathedral in Giulianova, Italy.

The Duomo San Flaviano is an octagonal Renaissance church built from the 1470s, with walls about two metres thick, corner pilasters, corbels and machicolations along the sides. A dome on a drum rises to an octagonal lantern, once covered in blue majolica tiles visible from the sea and now in semicircular terracotta tiles. The interior was stripped back to its 15th-century forms by restorations in 1926 and 1948.

Built from the 1470s, the octagonal church was first named S. Maria in Platea and took the name San Flaviano when the saint's relics were moved there in 1478. Its design is attributed to Francesco di Giorgio Martini, active at the same time on Giulianova's ducal palace and walls. Completed in the early 16th century with a rib vault rather than today's dome, it was restored in 1871, 1895, 1926, 1939 and 1948.

The church was first called S. Maria in Platea and took the name San Flaviano when the saint's relics were moved here in 1478. It is still the seat of the archpriest parish of San Flaviano. On the outer wall facing Corso Garibaldi, a war memorial of 1922 is crowned by an older bronze eagle by Ulderico Ulizio.

The octagonal church stands on the southern edge of Giulianova's old town, its south side joined to the houses that grew up against it from the 16th–17th century. The war memorial of 1922, crowned by Ulderico Ulizio's bronze eagle, is on the exterior wall facing Corso Garibaldi. The interior is bare after the restorations of 1926 and 1948, so look for the crypt beneath the church, covered by an umbrella vault on eight pillars.

The dome was once covered in blue majolica tiles that made it a landmark visible from the sea at a great distance; these were later removed and replaced with semicircular terracotta tiles. On the Corso Garibaldi side, a war memorial for the fallen of World War I has stood since 1922, crowned by an older bronze eagle by Ulderico Ulizio.