Complex sentence: The Old City walls were dismantled in 1912 however, and today only a very small portion remains, which has been transformed into a museum, the Dàjìng Gé Pavillon (上海古城墙和大境阁).
Split into simpler sentences: The Old City walls were dismantled in 1912 however. Today only a very small portion remains, which has been transformed into a museum, the Dàjìng Gé Pavillon (上海古城墙和大境阁).