Old hot air duct hatches

These mysterious hatches you can see around the church opened the hot air ducts which were used to heat the cathedral in the early 20th century. Back in the day the heating of the cathedral was done with 4 huge wood-burning furnaces that were situated in the basement of the cathedral. The early heating system was insufficient the heat up the large spaces of the cathedral and as a result the cold and humid. The constant humidity caused damage to the frescoes of the church and as such they had to be re-painted only 25-years after the cathedral was finished.

Nowadays these air ducts have become obsolete and remain in the church hall as a relic of the past.