The construction of the Notre Dame Cathedral began in 1163.
The Notre Dame is considering as the heart of the country of France in terms of travel distances. Look, for the bronze star in the cathedral square, this is the point that is used to make road sign travelling distances ;)

After a century of glory by being the French Kings cathedral (look for the French Kings emblem, the lily flower, inside the cathedral and the royal gallery above the doors from the exterior) The Notre Dame was deserted and become destroyed after the French Revolution.

It was the French writer Victor Hugo with his famous novel published in 1831, the Hunchback of Notre Dame,that saved the cathedral from being forgotten.

Things to see inside and outside the Notre Dame:

• The Cathedral's Gothic architecture
• The Bronze Star centre point of the country in terms of travel distances on the cathedral square
• Bible scene over the doors
• French Kings symbol and representation
• Louis XIII and Louis XIV Statue (near the altar of ND cathedral)
• Notre Dame stained glass
• Creepy atmosphere when you are inside :D

Things to see from Notre Dame's Towers:

• Gargoyles (used as a gutter to evacuate water and as the devil symbol for the last judgement in order to keep the believer on the right track and make them follow the church if they don't want to finish their day as one of those gargoyles).
• Sublime view over Paris

A sample of the Notre Dame Paris: 

How to get to Notre Dame: Cathédrale Notre-Dame - 6 Place du Parvis Notre-Dame, 75004 Paris

• M4, RER B-C Saint Michel Notre Dame
  M4 Cité
  M1-11 Hôtel de Ville
  Bus: 21-24-27-38-47-85-96
  Vélib' (City Bike): 4001 Arcole – 4003 Quai aux Fleurs
  Noctilien (Night Bus): N14-N21 Cité Palais de Justice, N15-N22 Cité Palais de Justice or Cité Parvis Notre Dame, N11-N12-N13-N14-N15-N16-N21-N22-N23-N24-N122-N144-N145 Châtelet

• Maps:
  
  

• Opening hours of the Notre Dame Cathedral, Price Free entrance

• Opening hours of Notre Dame Towers and Prices