One of Paris's most iconic buildings, the Notre-Dame cathedral, caught fire last night. The blaze destroyed the church's spire and damaged parts of the roof of the Gothic building which draws around 13 million visitors a year.

The 850-year old cathedral, which is also referred to as 'the forest', has a major flaw in its structure, which makes it highly flammable.

The structure of the entire building is made of timber, with an estimated 1,300 trees (52-acres of wood). The timber frames serve as the foundation for the 115-foot high roof, which is also made of wood.

This caused the fire to spread quickly and the spire of the cathedral to collapse not long after the fire began.

The reason for the fire remains unclear, but some believe it could have started due to the restoration-renovation work that was going on.

The Notre-Dame is famous for its unique gargoyles and priceless paintings, which firefighters are still trying to salvage.

"The fire is under control now and the main structure of the Gothic cathedral is saved from total destruction," said Notre Dame de Paris spokesperson, speaking on Tuesday morning (GMT +8).

Image credit: CNBC