China
Home to one of the most ancient cultures of the Eastern Hemisphere of Earth, and one of the most wizard-friendly. (The name is an Anglicization of the word Qin, pronounced "Cheen", after the first dynasty to unify all of China.) See the Wikipedia entry for much, much more information about everything Chinese except the wizardry.)
The Chinese cultures were for thousands of years the most persistently astafrith ones on the planet. What remains mysterious about this is exactly why this should have come to be. Whatever the reasons, wizardry was openly acknowledged in China as a fact of life from a very early time. References to it slipped completely casually into the great chuanqi or ch'uan-ch'i "marvel tales" of the Sung / Song dynasty, a genre of stories which appeared both as prose romances and operas. These sung and written works are the direct ancestors of the famous wuxia novel and film tradition -- tales of high chivalry which routinely also contain much wizardry entirely as a matter of course. (Crouching Tiger, Hidden Dragon would be a typical example of one of these stories, which mix swordsmanship, romance and wizardry without finding any of these elements more unusual than the others.)
This casual acceptance of the fact of wizardry -- if not always the harder details of how it worked -- has produced what is possibly the world's richest popular-culture tradition of stories about wizardry, the people who practice it, and how they interact with the world around them. Countless legends of Chinese wizardry exist across the entire spectrum of regional and national storytelling, ranging from tales of ancient days to more modern stories which are now routinely mistaken by literary critics from other cultures as "magic realism."
This extremely open culture and attitude may possibly the reason why an unusually high percentage of the wizards classified as the "world's greatest" have come from China, especially during the period of its greatest cultural flowering between the Han and Tang dynasties. Notable among these wizards were the wandering healer Fei Chang-fang; the specialist in animal mastery, Ge Hong; the strategist and tactician Kiang Tzu-ya; Ko Hsuan the "Ghost Catcher"; the "power meditator" and mystic T'ai-hsuan Nu, widely known as "the Lady of the Great Mysteries"; Mahku, the "People's Protector": the prodigy Tung-fang Shuo; and the unpredictable T'ang Kuang-chen, also known as "the Woman Who Flew on a Toad".
It should be mentioned in passing that over the past century or two, the original word for wizard, 巫师, wūshī, has developed some negative connotations in China. These may be due to cultural "creep" due to Westernizing influences, or possibly just a sense that the word is old and crude (it apparently derives from a fairly ancient word for woman, 巫 wū, referring to women who danced at temples to invoke the gods and acted as mediums through whom the gods spoke). The word for wizardry itself, 巫术, wūshù or "wizardly crafts", has most likely been suffering from the same problem.
(See also: National character in wizardry.)