These are the two plaques at Ostia Antica. The death and burial of St. Monica are mentioned in the Confessions of St. Augustine. We don't know where exactly she died or was buried at Ostia, but this is where the pilgrims gather to pray and to read from the Confessions.
With two Augustinian priests we stood in the rain and read book nine from the Confessions of St. Monica's death and burial being recounted by Augustine a dozen years later. It was amazing. The priest began to weep as he read each time. It would be a changed world if every eighteen year old would read the Confessions.