"中华世纪坛" can be translated as "Century Altar of China" or more commonly and idiomatically as "China Millennium Monument".
"Century Altar of China" directly translates the components of the name, emphasizing its significance as an altar or monument representing a century (though in this case, it symbolizes a broader era or millennium).
"China Millennium Monument" is a more widely recognized translation that captures the essence of the monument's purpose as a commemorative structure marking the new millennium (or a significant era in Chinese history).
In most contexts, especially when referring to this specific landmark in Beijing, "China Millennium Monument" would be the preferred and more accurate translation.