Mont Saint-Michel, a majestic Gothic treasure between tides

Mont St. Michel is a stunning Gothic styled Benedictine Abbey located between Normandy and Brittany. Originally on dry land, it became an island due to rising sea levels and erosion. Today, it is a popular tourist destination with less than 50 residents but over 3 million visitors annually. The Abbey, accessible by a challenging climb, is a medieval time capsule and was designated a UNESCO World Heritage Site in 1979.

What role does Mont St. Michel play in terms of tourism?

Why was Mont St. Michel classed as a UNESCO World Heritage Site?