Which retail design innovation did the Romans introduce in the 2nd century CE that is considered the world's first shopping mall?

Before modern shopping malls and e-commerce, ancient civilizations developed sophisticated retail systems that shaped commerce for millennia. From the agoras of Ancient Greece to the bustling markets of Mesopotamia, retail strategies emerged that would influence trade throughout history. This trivia explores a fascinating innovation in ancient retail design that revolutionized the shopping experience in the Roman Empire and continues to influence modern retail architecture.

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Trajan's Market (Mercatus Traiani), a multi-level complex with over 150 shops and offices
The Forum Venalium, a circular marketplace with specialized zones for different product categories
The Emporium Magnum, featuring the first known use of display windows and product demonstrations
The Mercatus Plebeius, which introduced the concept of seasonal sales and discount pricing structures