With reference to ancient South India, Korkai, Poompuhar and Muchiri were well known as

Korkai, Poompuhar, and Muchiri were major maritime trade hubs and ports of the Pandya, Chola, and Chera dynasties respectively during the Sangam Age, facilitating extensive commerce with the Roman Empire. While some of these locations served as secondary administrative centers, they are primarily distinguished as ports in historical texts, whereas the main inland capital cities were Madurai, Uraiyur, and Vanji. This question tests the core concept of Sangam Age economic geography and the identification of significant coastal commercial centers in ancient South India.