The restored 15th-century Holy Trinity altarpiece. MONTSERRAT T. DÍEZ (EFE)

The cathedral of Palma de Mallorca, which remains under construction ("it's always collapsing," complained the statesman Jovellanos in the early 19th century), has just retouched its roots: the small chapel-and-vestry dating back to the early 1300s that was the germ for the larger building, which was itself built over the mosque of Madina Mayurqa.

Church officials called the chapel "a treasure" and "a crucial spot" where the first stones were laid for the great cathedral.

The reopening of the chapel served to mark the 666th anniversary of the "dedication" of this building in 1346. Dean Joan Bauzá joked that he hoped the triple digit would be "an omen of good luck, not of the wild beast of the Apocalypse," a reference to the fact the number 666 is associated with Satan.

For two days, visitors will be allowed to enter the small chapel, which has been returned to its original bare state and will be used for cultural events.

For the first time, the cathedral will also grant visitors access to its terraces.

In a few months, after the bells and the medieval structure that contains them are also restored, church officials hope to organize public tours of the upper portion of the cathedral, where the sky and the sea of Palma de Mallorca are framed by the pinnacles, the stained-glass windows and the giant rose window.

However, potential visitors should bear in mind that reaching the rooftop involves climbing 200 steps of one of the narrow spiral staircases inside each of the towers, where the walls still show medieval graffiti made by the refugees and fugitives who once hid out here.

The cathedral receives around a million visitors and worshippers a year, say church officials. Many people come to see the ceramic chapel recently created by artist Miquel Barceló, as well as the 1900 reforms made by Gaudí.