Built in the 16th century in the historical centre of Castiglione della Pescaia, this church is connected to a striking 20th bell tower that makes it impossible to miss - and you won't want to either because inside are some extremely valuable relics which belonged to the town's patron saint Guglielmo di Aquitania - they're not everyone's cup of tea, but they're definitely worth a look.
The church itself was carved from rock and built on top of another 11th century building. Above the entry, which opens on one side, is a walled lintel built in the early Middle Ages and carved with symbols of the Gospel.
The single nave and truss roof interior isn't much, but the work by Nasini titled 'Santi Guglielmo e Petronilla che invocano la Madonna a protezione del paese' ('Saints William and Petronilla invoking the Madonna to protect the country') - is breathtaking.
Another fascinating sight to say the least are the remains of Guglielmo di Aquitania, which adorn the altar in a 17th century silver urn along with some of his personal belongings.