San Giovanni in Conca is a crypt of a former basilica church in Milan. The basilica dates from the 4th cent., and was located in a residential quarter of the ancient city. Remains of the mosaic pavement of this original edifice are now in the Archeological Museum of Milan. The church was rebuilt in the 11th cent., but was destroyed by Frederick Barbarossa's troops in 1162. It was again reconstructed in the 13th cent. and later became the private chapel of the Visconti rulers of Milan. Bernabò Visconti had it connected to his new grandiose palace through a super-elevated walk, and was buried here in a monument by Bonino da Campione which is now in the Sforzesco Castle.