Fondo d'Oglio Crater

Where it is

Fondo d'Oglio opens out in the upper part of the Bosco della Maddalena (Maddalena Wood), on Monte Rotaro, just below the highest point of the pine wood. It is the best-known crater in the Casamicciola Terme area and is easy to reach: from Via Cretaio you can drive to a clearing, closed to traffic, from which you can look down into the hollow.

How it formed

INGV's Vesuvius Observatory places Fondo d'Oglio within the history of the Rotaro complex, a volcano built by at least nine eruptions over the last ten thousand years. In an intermediate phase, a lava dome formed in the area of the present-day Bosco della Maddalena; its lavas are still exposed inside the crater. Later Strombolian activity, consisting of repeated explosions that hurl out clots of lava, partly demolished the dome and opened the crater, depositing the so-called Fondo d'Oglio scoria, clearly visible at the entrance. Later still, a low-energy explosive eruption from a vent slightly to the north-west laid down the Bosco della Maddalena pyroclastics, which are exposed mainly inside the hollow.

Popular sources give a diameter of about 350 metres and a depth of 127 metres. Volcanic “breadcrust” bombs, fragments of lava that cooled in flight and cracked on the surface, and blocks of trachyte were once easy to find on the floor: today they are a heritage to be admired and left where they are.

The name

The origin of the name is not documented with certainty; according to one local interpretation it recalls the “bottom of a jar”, an image that aptly describes the deep, enclosed hollow.

Vegetation

The crater is completely covered by woodland: holm oaks, chestnuts and pines on the rim, Mediterranean scrub inside. In the hollow, sources report unusual species such as the “dente di cavallo” or fumarole papyrus (Cyperus polystachyos), mosses of tropical origin and the fern Pteris longifolia. In the centre of the crater grows a hop hornbeam, a tree usually associated with mid-altitude mountains, which local tradition surrounds with legends.

How to get there

• From above: from Piazza Marina via Corso Luigi Manzi, Via Monte della Misericordia and Via Cretaio, to the clearing above the crater.
• From below: from the Castiglione entrance to the Bosco della Maddalena, walking up the Maddalena Trail.

From the clearing a path follows the crater rim just below the ridge and descends to the floor. From here you can continue towards the Montagnone along the Fondo d'Oglio and Montagnone trail.

Useful tips

The descent has steep stretches on earth and lapilli: hiking boots are needed, ideally with poles. There are no drinking fountains, so bring water. The Monte Rotaro fumaroles are also nearby: observe them from the path.