From the 12th to the 13th century, Konya, the capital of the Seljuk Turks, ranks as one of Turkey's most important cultural centers. During this cultural, political, and religious development period, the mystic Mevlana Celaleddin-i Rumi founded a Sufi order known in the West as the Semazens. Mevlana's striking green-tiled mausoleum is Konya's most famous building. The former dervish school attached to the mausoleum now serves as a museum with manuscripts of Mevlana's works and various Sufi-related artifacts of the order. The Şeb-i Arus (Wedding Night) ceremony, held every year in the first half of December in memory of Mevlana Celaleddin-i Rumi, is a mesmerizing performance of controlled, trance-like spins or whirling dervishes by men in white robes.