求翻译：天坛，中国现存的天坛共有两处，一处是西安天坛，另一处是北京天坛，其中属北京天坛较为著名。天坛是皇帝用来祭天、祈谷的地方。是什么意思？

The temple, there are two extant Temple in China, one is the Xian Temple, another is the Temple of heaven in Beijing, of which the temple is more famous. Temple of heaven is the place where Emperors used to worship heaven and pray for the Valley.