What is a Lararium?
A Lararium is the sacred place of the home where offerings and prayers are made to the Gods.
In more affluent Roman homes, such as private villas, the main Lararium altar was usually set in the Atrium (front reception room, near the front door). In smaller Roman homes which might not have an atrium, such as insula apartments, the Lararium was most often located near the hearth (the kitchen or place of a central fire). But a house could have several minor Lararia as well, indoors (especially in the bedrooms) or outdoors.
A lararium, properly speaking, is a shrine for the Lars. During the Republic there does not seem to have been any statues used to represent the Lares, since they were considered more as ancestors. The death masks of ancestors were stored in boxes, hung on a wall near the entrance of the house, and it might possibly be that lararium meant something like a foyer where these were kept. Today it would be comparable to having photographs of your ancestors at your lararium. Beginning in the fourth century BCE certain patrician families assumed divine heritages and thus may have begun to include images of a Lar familiaris such as Venus, but these would still have been regarded there as an ancestor.
Religio Romana 