1661: Athanasius Kircher discovers the ruins of a church in Rome said to have been constructed by the Emperor Constantine on the site of Saint Eustace's vision (later reconstructed as the Santuario della Mentorella).
Other events
1667: Henry Howard donates the first of the Arundel marbles to the University of Oxford (displayed in Ashmolean Museum).
Deaths
1661: Famiano Nardini, Italian archaeologist (b. c.1600)