Five years on, investigators are still trying to solve the mystery of what started the blaze at the French religious and cultural landmark.

Notre Dame Cathedral, is set to reopen to the public on Sunday (December 8) after a five-year restoration following a devastating fire, stands as a jewel of Gothic architecture, a symbol of Paris and a tourist mecca.

After five years of speedy reconstruction work, Notre Dame will soon reopen. But the architect formerly in charge of Cologne Cathedral in neighboring Germany fears that things are moving too fast.