Many people think of this city as the cultural capital of the country.

think 是动词，意思是"认为、思考"。 of 是介词，在这里与 think 搭配使用，表示"关于"或"对...的看法"。 as 是介词，意思是"作为"，在这里表示"把...看作..."。 think of...as... 是一个固定搭配，意思是"把...视为..."或"认为...是..."。