Complex sentence: The basement of Béthanie, once used as a wine cellar and dry goods storage, has now been converted into a museum displaying historical items of Bethanie and the French missionary's activities in Asia throughout the past 300 years.
Split into simpler sentences: The basement of Béthanie was once used as a wine cellar and dry goods storage. However, it has now been converted into a museum displaying historical items of Bethanie and the French missionary's activities in Asia throughout the past 300 years.