Complex sentence: The Hainburger Au is a large naturally occurring flood plain bordering the River Danube at, and upstream of, Hainburg in Lower Austria and a short distance to the east of Vienna's main airport.
Split into simpler sentences: The Hainburger Au is a large naturally occurring flood plain bordering the River Danube at, and upstream of, Hainburg in Lower Austria. It is a short distance to the east of Vienna's main airport.