Muslim architecture incorporated Roman and Byzantine elements primarily because the Romans and Byzantines once ruled some Muslim lands. After the Islamic conquests, many regions that came under Muslim control had significant Roman and Byzantine architectural influences due to their prior rule.
This incorporation occurred as Muslim architects and builders encountered existing structures and styles, which they adapted and reinterpreted to fit Islamic culture and religious practices. Additionally, the sophisticated engineering techniques and monumental designs of Roman and Byzantine architecture influenced the development of Islamic architectural forms, leading to a rich blend of styles that characterized the architecture of the Islamic Empire.