That could be where the den comes in. I’m convinced the hikers didn’t build that...maintenance, testers ...could’ve been housed there or hid sled there???
In so far as the terrain:
"Sever" transported mail [[in areas where earlier the use of any transport, except dog sleds, was impossible.]]. The average distance of the Severus-2 aerosleigh was 12-15 thousand kilometers per year with an average speed of 30-35 km / h on postal routes. Routes passed through virgin snow, hummocked ice in the frost to 45-50 ° C. Aerosans worked along the Amur River, served the villages along the banks of the rivers Lena, Ob and Pechora. They carried out regular mail and passenger flights in the regions of Siberia, the Far East and Kazakhstan.”
Someone was there...how they got there or reason is an issue, I’m pointing ou it’s possibe, without using a dog sled or helicopter...