The site of Arrillor is a cave of the Middle Palaeolithic, located to the SE. Mount Gorbea, which is located in the Spanish municipality of Cigoitia (Álava). The environment of Arrillor is lithologically composed of reef limestones, which generate a karst with numerous caves.

It is a linear cave of about 150 meters in maximum length, oriented towards the W-E, with two corridors marked at its ends. Around both, we find two entrances, one from the ravine of Asunkorta and the other, the main one, from that of Errekaseku. At various levels, several prehistoric tools, fauna hunted by man, and even a tooth of Neanderthal man (the only known vestige in the province of Álava) have been discovered; most of the occupations belong to the Middle Palaeolithic -Mousterian- and residually from the end of the last glaciation -Magdalenian-.

Evidence of human occupation has been found: Small carbonaceous remains along with numerous skeletal remains and lithic industry. The presence of an upper second molar of human milk from an individual aged 9 to 13 years is important.