The intricate, labyrinthine system of underground tunnels that constitute the catacombs can stretch out over many miles. The actual burial places are niches cut out in the tunnel-walls.
These niches are called loculi and can also contain more than one person at the time. For the first burials were the bodies were simply wrapped in a shroud and there was no coffin. The loculi were closed off with a marble plate or, more often, simple tiles. An inscription would sometimes give a name and oil lamps and perfumed vases were placed next to the tombs.
The tombs were arranged in rows on top of each other. The word “cemetery” was take from Greek: Its meaning, resting place, indicated the Christians’ faith in the body’s resurrection.
Other types of tombs beside the loculi were:
- Arcosolium: A larger niche, with an arch over it and an horizontal tomb-covering. Usually contained whole families. More popular in the 3rd and 4th centuries.
- Sarcophagus: A coffin made of stone or marble and adorned with reliefs and inscriptions.
- Forma: Tomb dug into the floor of a cubiculum, gallery or crypt, often to be found near the tombs of martyrs.
- Cubiculum: Small rooms serving as family tombs, often decorated with frescoes.
- Crypt: Bigger rooms, that were converted into small underground churches. These martyrs tombs were adorned with paintings and mosaics.
The catacombs were dug by the so-called fossores (a guild of gravediggers). The earth was carried away through sky-lights called lucemaria. After the completion of a hallway the lucemaria were kept open and served as a means of ventilation.