Final answer:
The Stupa architectural style, which evolved into the Pagoda style, was imported into China from India during the Han Dynasty and was part of the spread of Buddhist architecture.
Step-by-step explanation:
The architectural style imported into China from India during the Han Dynasty was the Stupa, which eventually evolved into the Pagoda style. This structural form was part of the Buddhist architectural heritage that spread with the religion from its Indian origins. The Stupa is a mound-like or hemispherical structure containing relics and is used as a place of meditation. The architectural innovations during the Gupta period, with the integration of architecture, sculpture, and painting in sites like Nalanda University, indicate the kind of complex and ornate buildings that influenced East Asian architecture.
A significant factor in this architectural transmission was the high regard for sacred buildings and religious sites, evidenced by various cultures around the world erecting imposing structures like temples, churches, mosques, and pagodas, as described in section 7 of the reference material. It also included the employment of sculptures, special trims, architectural configurations, and unique materials, such as those used in the Gupta period structures, to enhance the religious and aesthetic appeal of these sacred spaces.