Smolenskaya on the Arbatsko-Pokrovskaya Line
Before going underground, look at the large arched windows of the entrance hall and check the line colour on the signs.

Getting there
No. 53 Arbat › End of Old Arbat › Smolenskaya Square › Line 3 entrance hall
Walk to the end of pedestrian Arbat. Use the marked crossings and follow signs for Smolenskaya on blue Line 3. Complete the quest outside the entrance before heading down.
The same station name appears on two lines here. Check the colour and number on the signs to find the right entrance.
Open in Yandex Maps · Route in Yandex Maps
History
Two Moscow metro lines have a station named Smolenskaya. For this walk, you need the deep station on the Arbatsko-Pokrovskaya Line. Trains began running along the deep section from Ploshchad Revolyutsii to Kiyevskaya in the spring of 1953. One short ride will take you from the lanes of the Arbat to the river.
Sources
55.74806, 37.58381
Go to stop · The clock tower of Kiyevsky Railway Station