Complex sentence: Around 928 or 929, during a campaign against the Slavs, King Heinrich I built a castle on a hill on the Elbe, which was named after the Meisa, a nearby stream.
Split into simpler sentences: Around 928 or 929, during a campaign against the Slavs, King Heinrich I built a castle on a hill on the Elbe. This castle was named after the Meisa, a nearby stream.