Passage: Ruslan, having come upon a foggy desert strewn with weapons and bones from a past battle, wonders at the cause of this scene and whether he, too, may end up the same way. He chooses a new shield and spear from the ground to replace his broken weaponry, but cannot find a sword heavy enough to complete his new set of armor. When the fog lifts, a giant Head is revealed and blows through its lips to bring up a storm so as to drive Ruslan away. When Ruslan strikes the head with his spear, the Head falls back and reveals a sword underneath. He takes it and asks the Head whence it came. As it is dying, the Head explains that it once was a giant, and his dwarf brother is the evil sorcerer Chernomor. The sword was destined to kill both of them; so, in order to forestall fate, Chernomor tricked the giant, beheaded him, and flew his live head away to the distant desert to keep the sword protected underneath it. With the sword now in Ruslan's hands, the Head calls for vengeance on Chernomor.

Question: Where did Ruslan find evidence that there had been a previous fight?
a foggy desert