Following the fortuitous discovery in 2014 by a Turkish archaeologist of the foundations of a Byzantine basilica submerged in Lake Iznik, not far from Istanbul, an international team of French, Turkish, Swiss and American researchers is investigating in close collaboration with the team of Turkish archaeologists to try and retrace the history of this mysterious basilica. Why is it submerged? What tragic fate lurks at the bottom of this lake? What could the excavation of such an edifice reveal? There's a reason why these remains have aroused the passionate and enthusiastic interest of an entire international scientific team: its location, Iznik. This is the current Turkish name for the ancient Roman city of Nicaea.