What institution remained powerful from Roman times to the 16th century?

The Catholic Church emerged as a central institution in Europe during the Roman Empire and maintained its influence throughout the medieval period and into the 16th century. From its early establishment as a significant spiritual authority, the Church became deeply entwined with political power, social structures, and cultural life across Europe. It wielded considerable authority over not only religious matters but also governance and moral guidance.

Throughout the centuries, the Catholic Church played a crucial role in unifying diverse European populations under a common religious framework, which helped to stabilize societies that were often fragmented by local loyalties. It established a vast network of institutions, including monasteries and cathedral schools, which were instrumental in preserving knowledge and fostering education during the Middle Ages. The Church's power was further solidified through its ability to influence monarchs and its involvement in various political conflicts, such as the investiture controversy.

While other institutions like the monarchy and nobility held significant power, the Church's influence was unique in terms of its longevity and pervasive impact across different facets of life and governance through the centuries leading up to the Reformation in the 16th century. The rise of the mercantile class, while significant in later periods, did not have the sustained impact that the Catholic Church maintained over such