the temple of farthest China

A temple at the far end of China, described by Abu Ubayd al-Bakri as reported by Ibn Fadl Allah al-Umari. ¹

It is a round house with curtains and doors. Inside it is a great seven-sided dome. ¹

In it is a well with a seven-sided mouth. The description says that whoever bends over its mouth will be drawn into it. Over its mouth is a kind of collar, written in Sindhi script, which says that it leads to the store of the first books, the history of the world, the sciences of the heavens and the treasuries of all the desires of this world. ¹

The exact site of the temple, its date, and anything that supports this description: an additional source is needed.