 In 1889–1890 he visited Lipetsk and completed there two schools, a hospital and a prison chapel – at the age of 23.Back in Moscow, Mashkov completed over a dozen buildings still in his twenties, and his masterpiece – the "Sokol" – at the age of 36.Mashkov's "Sokol" (Falcon) building is unique not only for his career, but to Moscow Art Nouveau in general.