Complex sentence: When Filene's closed, the Boston Landmarks Commission unanimously voted to protect the two oldest buildings that housed Filene's, the main 1912 store and a 1905 former glassware and china seller's building on the opposite corner.
Split into simpler sentences: When Filene's closed, the Boston Landmarks Commission unanimously voted to protect two of the buildings that housed Filene's. The two oldest buildings were protected including the main 1912 Filene's store building and a 1905 former glassware and china seller's building on the opposite corner.