The Silk Road represents an early phenomenon of political and cultural integration due to inter-regional trade. In its heyday, it sustained an international culture that strung together groups as diverse as the Magyars, Armenians, and Chinese. The Silk Road reached its peak in the west during the time of the Byzantine Empire; in the Nile-Oxus section, from the Sassanid Empire period to the Il Khanate period; and in the sinitic zone from the Three Kingdoms period to the Yuan dynasty period. Trade between East and West also developed across the Indian Ocean, between Alexandria in Egypt and Guangzhou in China. Persian Sassanid coins emerged as a means of currency, just as valuable as silk yarn and textiles.