Monte Cairo (1,669 m) is a mountain in Lazio, overshadowing both the Abbey and the town of Monte Cassino, 5 kilometres to the south. The ancient 'Mons Clarius' was so called because originally a temple dedicated to Apollo (Clarius) stood where the Abbey of Monte Cassino now stands. This massif, commonly referred to as the Monte Cairo group, stretches eastwards from the upper Melfa valley over roughly 15–20 km, as can be seen on regional topographic maps and route descriptions.