This is probably the longest available route alongside and through The Caucasian Biosphere Reserve - 70 km from the North side along the Eastern border by the Big Tkhach through the Damn Gate and then 67 km to the South by the route #8 to Rosa Khutor. 

Route Link: https://connect.garmin.com/modern/activity/7448339141

Start: North end of Terror Lake on Kodiak Island where the road meets the lake.

End: Trailhead for Kashevaroff Mountain.