Which type of Roman classical building served as covered markets and law courts?

The type of Roman classical building that served as covered markets and law courts is the basilica. In ancient Rome, the basilica was a multifunctional structure that typically featured a large central nave with side aisles and was often used for various public activities, including commerce and legal proceedings. The architecture of the basilica allowed for a spacious and well-lit environment conducive to these functions.

Basilicas were significant in urban life, acting as centers of social, political, and economic activities. The design facilitated large gatherings, making them ideal places for courts of law to conduct hearings and markets to operate, especially in bustling cities. The term "basilica" later evolved in Christian architecture, but the foundational concepts from Roman times influenced its design and function.

In contrast, the other building types listed had different primary uses. The curia was primarily a meeting place for the Senate, insulae were multi-story apartment buildings for housing, and domus were private residences for wealthy individuals. Thus, while each of these plays an important role in Roman architecture, only the basilica aligns with the functions of serving as covered markets and law courts.