The Dry Tree (or Tree Solitary) is a legendary tree. It was recorded first by Marco Polo, somewhere in northern Persia. According to Polo, it was the only tree within hundreds of kilometres of desert. According to legend, the Dry Tree marked the exact site of a great battle between Alexander the Great and Darius. It is not known whether this "great battle" refers to the Battle of Issus or the Battle of Gaugamela. The purported location—somewhere in Khorasan, near the border with present day Turkmenistan—is also impossible to ascertain, because Darius had already been assassinated when Alexander reached these regions.