Now that we slogged through the sandy hike to Mont Saint-Michel, we spent the next day hiking up the interior.  Mont Saint-Michel started as a monastery (monks only) in the 7th century, became an abbey in the 14th century (monks and nuns), then a prison during the French Revolution (1789-1799), then back to an abbey.  Now it’s used both for religious experiences and tourism, and has been a UNESCO World Heritage Site since 1979.