The House of Annius was built in the Hadrianic period. Originally it was connected with the Magazzino dei Doli (I,XIV,3) to the north and the Edificio a tabernae (III,XIV,1) to the east, through windows and doorways.

In the west facade, along Via di Annio, on the springing of a balcony, are three terracotta slabs with the words OMNIA FELICIA ANNI in tabulae ansatae: "The business of Annius is doing well". The letters of the third word are filled with small pieces of pumice. Below these words are two terracotta reliefs. On one a man is depicted between storage jars (dolia), on the other we see a boat with storage jars. The reliefs are another indication that there was a relation between this building and the building with dolia (for wine or olive-oil) to the north. At the north end of the west facade is an external staircase. A huge travertine block is embedded in the facade to the north of the staircase. In the south facade (on the Cardo degli Aurighi), at the intersection with Via di Annio, is a curved wall-niche, high up in the wall. It once contained a statue of a deity.

Originally the building seems to have had a commercial function, with shops on the Cardo degli Aurighi and Via di Annio, and with work areas connected by many and often wide passages. Basically the interior consists of piers supporting cross-vaults. Room 14 was a bar, with a bar counter in the south-west and a buried storage jar (dolium defossum) in the south-east corner. In the later second or in the third century many passages were blocked. Sometimes large floor-niches were created, giving a more spacious impression. It seems that two apartments were created: rooms 4-8 and 9-13. The walls were decorated with red and yellow paintings on a white background. We can still see architectural motifs, vegetative motifs, and a bird.

Could our Annius have been Annius Serapiodorus, a producer of oil-lamps who was active in Ostia in the Severan period?