Truely epic in magnitude, and the only man made structure visible from space, China's Great Wall is in fact a series of different walls that were constructed at different periods of history. Construction of the first wall began in about 200 BC, since when it has been expanded to cover huge swathes of the country. Without doubt, China's most impressive tourism attraction is the Great Wall.
The Great Wall of China.
The Great Wall in Style
The Great Wall can be visited from a range of destinations as it covers so much of China (and parts of Mongolia too). The above photo gives an idea of quite how impressive an attraction it is. A common and relatively simple way to visit is by day tour from Beijing, though these are some of the more touristy sites such as Badaling and Juyongguan. Generally speaking, the further one travels away from Beijing, the less touristy, and more authentic the experience. Those with plenty of time on their hands could consider taking extensive treks along the route of the wall for the most memorable of experiences possible in China.
Beijing is the logical place to visit in conjunction to the Great Wall of China. You might also consider visiting any number of other tourism attractions such as Shanghai, Hong Kong, Hainan or even Tibet.