You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Genghis_Khan

Context:
On October 6, 2004, a joint Japanese-Mongolian archaeological dig uncovered what is believed to be Genghis Khan's palace in rural Mongolia, which raises the possibility of actually locating the ruler's long-lost burial site. Folklore says that a river was diverted over his grave to make it impossible to find (the same manner of burial as the Sumerian King Gilgamesh of Uruk and Atilla the Hun). Other tales state that his grave was stampeded over by many horses, and that trees were then planted over the site, and the permafrost also did its part in hiding the burial site.

Question:
What kind of water body is rumored to be obscuring Genghis Khan's burial site?

a river