The R21 highway runs from Saint Petersburg, south of Lake Ladoga to Petrozavodsk, Kondopoga, Medvezhyegorsk, Segezha, Kem, Loukhi, Kandalaksha, Polyarnye Zori, Monchegorsk, Olenegorsk, Kola and ends in Severomorsk.

It passes the Arctic Circle a couple of kilometers south of the border of Karelia and the Murmansk oblast, north of Loukhi.

In the Republic of Karelia, the landscape through which the R21 runs is mainly forest (birches), rivers and lakes.

In the Murmansk Oblast, the highway runs for the most part through the Kola Peninsula, a severely polluted area.

The landscape here is more open and consists partly of half-tundra.