Where is it in Moscow?

Tverskoi Boulevard, No. 25. The building off Tverskoy Boulevard, beyond a small garden with a wrought iron fence (see below), was the birthplace not of Griboyedov, but of Hertzen (it's Hertzen's statue, the statue of Griboyedov is at Chistye Prudy!).

the fence

In the 20s there were several writers' organizations housed here: RAPP (The Russian Association of Proletarian Writers), MAPP (The Moscow Association of Proletarian Writers), and LOKAF (The Literary Union of the Red Army and Navy). There was indeed a writers' restaurant here until 1931. In the 1930s the building became what it is today: the Literary Institute, today named for Maxim Gorky.