The finest example of Carolingian architecture in the region, St. Martin's Church is the most ancient church in Austria still (more or less) in its original form. Constructed by Charlemagne during the 700s, it used the ruins of an ancient Roman wall for parts of its foundation. Its interior is decorated with frescoes, several fine examples of baroque art, and a 15th-century Gothic choir. Restored in 1948, the church stands a 10-minute walk west of Hauptplatz, in a neighborhood filled with commercial buildings. A covered passageway connects it directly to the Linzer Schloss . Although it's not open to the public, the church is almost always included as part of the official tours sponsored by the Linz tourist office (tel. 0732/70701777).