Complex sentence: In the upper level are its deceased or deified members including Divus Augustus, surrounded by Drusus the Younger (son of Tiberius) and Drusus the Elder (brother of Tiberius) flying on Pegasus.
Split into simpler sentences: In the upper level are its deceased or deified members including Divus Augustus. The surrounding figures may be Drusus the Younger (son of Tiberius), and Drusus the Elder (brother of Tiberius) flying on Pegasus.