Saint-Maurice is the largest medieval church in the old town, a fifteenth-century Dominican foundation just steps from the Palais de l'Île. The exterior is plain, almost barn-like; the interior is unexpectedly wide and high, with a single great nave covered by a wooden ceiling and lit by big late-Gothic windows.
The most striking feature is the trompe-l'œil Renaissance funerary fresco of Philibert de Monthouz (1458) on the north wall — a painted bier that fooled visitors for centuries into thinking a real shrouded body lay there. Several other fifteenth- and sixteenth-century paintings line the side chapels. Free; open daily.