Facebook CEO Mark Zuckerberg visited the campus of China's largest search engine Baidu on Monday. Baidu confirmed that Zuckerberg had made the visit, but it wouldn't comment on what they were talking about. Zuckerberg's girlfriend is Chinese and has family in the country. In another interview with the media, the Facebook CEO said he has a personal interest in China and even takes daily Chinese language lessons. Facebook, however, is currently blocked in China, along with other popular U.S. sites such as YouTube and Twitter. China's government routinely monitors and block websites for politically sensitive content.