Trajan's Market surmounted by medieval Torre delle Milizie, Rome

Trajan's Market (Latin: Mercatus Traiani, Italian: Mercati di Traiano) is a large complex of ruins in the city of Rome, Italy, located on the Via dei Fori Imperiali, at the opposite end to the Colosseum. The surviving buildings and structures, built as an integral part of Trajan's Forum and nestled against the excavated flank of the Quirinal Hill, present a living model of life in the Roman capital and a glimpse at the continuing restoration in the city, which reveals new treasures and insights about Ancient Roman architecture.
Thought to be the world's oldest shopping mall, the arcades in Trajan's Market are now believed by many to be administrative offices for Emperor Trajan. The shops and apartments were built in a multi-level structure, and it is still possible to visit several of the levels. Highlights include delicate marble floors and the remains of a library.
Trajan's Market was probably built in 100-110 AD by Apollodorus of Damascus, an architect who always followed Trajan in his adventures and to whom Trajan entrusted the planning of his Forum, and inaugurated in 113 AD. During the Middle Ages the complex was transformed by adding floor levels, still visible today, and defensive elements such as the Torre delle Milizie, the "militia tower" built in 1200. A convent, which was later built in this area, was demolished at the beginning of the twentieth century to restore Trajan's Markets to the city of Rome.

more on https://en.wikipedia.org/wiki/Trajan's_Market , https://en.wikipedia.org/wiki/Torre_delle_Milizie