The castriño de Conxo (Conxo's small castrum) is located between A Rocha and the city of Santiago, at the parish of Santa María de Conxo next to the N-550 road (coming from Santiago towards Pontevedra), near the street by the name of Volta do Castro.
It is a castro culture settlement typical of the Iron Age in the northwest of the Iberian Peninsula. Although its existence is little known, the area is named after it. Currently all it can be made out is what might have been an oval-shaped enclosure, where handmills and pottery were unearthed. They have been dated between the 7th and the 1st century BCE, although we cannot determine when exactly within this wide range of time.
What really made the Castriño famous was the presence of a peculiar granitic slab with prehistoric engravings or petroglyphs.