Alum Trail (Sentiero dell'Allume)

A trail between nature and industrial archaeology

The Sentiero dell'Allume (Alum Trail) tells a little-known chapter of Ischia's history: the mining and processing of alunite, the mineral from which alum was obtained, a substance once prized for dyeing textiles and tanning hides. The route follows the old Via Crateca, which farmers called the “via dei carri” (cart road): along this road the mineral was carried down from the mining areas to the processing sites and then to the port of Casamicciola.

The route

According to the fact sheet for the hike offered on the island, the trail starts from Piazza del Fango, in the village of Fango in Lacco Ameno (150 m), and ends at Piazza Maio, in Casamicciola Terme (130 m). It is about 8.4 km long, with about 500 metres of ascent and the same of descent, takes about 3 hours and is graded E (hiking). The main stages are:

1. Fango (150 m): the first stretch is now largely a road open to traffic, lined with dog roses, valerian, broom, myrtle, heather and mastic.
2. Monte Cito (220 m): the fumarole field, where the ground is coloured white, purple and deep yellow. It was one of the places where alunite was mined.
3. Piazza de La Pera, known as “Caulare” (380 m): a plateau among the chestnut trees, paved with green tuff, where the processing works stood. The name recalls the boilers (caldaie) used to treat the mineral; the best-preserved tank measures about 5 metres in diameter and 1 metre in height.
4. Piazza Santa Barbara (160 m): the trail descends through the chestnut wood towards upper Casamicciola.
5. Piazza Maio (130 m): the old centre of upper Casamicciola, from which you can reach the historic spa areas of the Bagni and La Rita.

Along the way you can still see processing waste, stones foreign to the local geology, and the “parracine”, green tuff dry-stone walls built without mortar to let rainwater drain away. In places the old road has been diverted over time.

Why there was alum here

The fumarole field of Monte Cito lies along active faults, up which acidic, sulphate-rich hydrothermal fluids rise. Their contact with the volcanic rocks transforms them into alteration minerals, including alunite. The Monte Cito fumaroles are still among the hottest on the island today: the Civil Protection Department gives maximum temperatures close to 100 °C.

Before you set out: trail conditions

Before setting out, check with the Town Council of Casamicciola Terme or local guides on whether the trails above the town are passable, and always respect any access bans.

How to get there

Fango, a hillside village in Lacco Ameno, can be reached by road from the centre of Lacco Ameno. On arriving at Piazza Maio, walk down to Piazza Bagni and the centre of Casamicciola. The trail can also be walked in the opposite direction, starting from Piazza Maio.

Useful tips

• Hiking boots and clothing, plenty of water.
• Near the fumaroles, stay on the path: the ground is hot and unstable.
• Avoid the middle of the day in summer and the days after heavy rain.

A shorter variant in the same area is the Celario – Monte Cito – Crateca trail.