What is the term for a chapel in the Basilica that housed the Legion's standard or aquila?

The term for a chapel in the Basilica that housed the Legion's standard or aquila is "sacellum." This term specifically designates a small shrine or chapel, often used in a religious or ceremonial context, where sacred objects, such as the aquila — the eagle standard of the Roman Legion — would be kept. The sacellum was significant as it served as a place for worship and reverence, reflecting the importance of the standard for the soldiers’ morale and identity.

The other terms do not specifically refer to this function. "Templum" generally refers to a larger temple structure dedicated to gods or deities and is not limited to military standards. "Aedes" is another term for a temple, typically larger and more public than a sacellum. "Curia" refers to a meeting place or assembly room, particularly for the Senate or political gatherings, rather than a specific religious site for housing the standards. Therefore, understanding the unique role of the sacellum clarifies its connection to Roman military culture and religious practices.