Final answer:
Emperor Justinian constructed the Hagia Sophia in Constantinople in 538, which was a symbol of his power and the grandeur of the Byzantine Empire.
Step-by-step explanation:
The church that Emperor Justinian built in Constantinople in 538 was the Hagia Sophia, also known as the Church of Holy Wisdom. This magnificent structure was a significant architectural feat of its time and represented the power and wealth of the Byzantine Empire. Decorated with Greek iconography initially, it was the main cathedral and a central point in the city. Justinian's dedication to his faith and to the display of his imperial might was evident in the construction of the Hagia Sophia, which stood next to the imperial residence and the hippodrome. Over time, the appearance of Hagia Sophia evolved, especially during the Iconoclastic Controversy when figural mosaics were added, enriching its interior decoration and intertwining it with the theological and political changes of the era.