The Surgeon’s House in Rimini, Italy, is a Roman 2nd century CE house of a military doctor named Eutyches. After the decay of the building, in the 6th century CE, the area was used as a burial site as evidenced by some tombs discovered, some of which damaged the underlying floors [1080×1350]

Is that concrete or stone under the burial?

Just trying to imagine the chain of events… Building fell into decay, mosaic was probably buried. Someone dug through the mosaic and the stone layer beneath until they couldn’t dig anymore. Seems like an inefficient burial but no telling what was happening in the area.