The Darwish Forest is located somewhere in proximity to the border of the U.S.S.R. and Finland. The Darwish Forest was one of the points along the route that Steve Austin took to infiltrate the nation where Leon Jackson and his son Alex were residing. Jackson had defected to that nation(presumably the U.S.S.R) but wanted to return to the United States.
Oscar Goldman's instructions to Steve Austin were as follows:
You will be taken by Army transport to within 80 miles of the Darwish Forest. From there you'll be flown by private plane, just before dawn, to within five miles of the mansion where they're holding the Jackson's.
Additional information that may locate the Darwish Forest is the single escape route mentioned. After securing the escape of the Jackson's, Austin original plan for exfiltration was to use an abandoned mine shaft northwest of the mansion that passed under the Finnish Border.