The author of Uedinyonnyi domik na Vasilievskom ("The Secluded Small House in the Vasilievski Island," 1829), V. Titov visited Pushkin at Demut's Hotel:

Не желая, однако, быть ослушником ветхозаветной заповеди "не укради", [Titov] пошёл с тетрадью к Пушкину в гостиницу "Демут", убедил его прослушать от начала до конца, воспользовался многими, поныне очень памятными его поправками и потом, по настоятельному желанию Дельвига, отдал [the story] в "Северные Цветы". (Hodasevich, "Pushkin's St. Petersburg Tales")

In 1829, staying at Demut's Hotel, Pushkin wrote Poltava (cf. Byron's Mazeppa) and began Chapter Eight of Eugene Onegin. From VN's EO Commentary (III, p. 269):

The oldest hotel in St. Petersburg was the Hotel Demut, on the Moyka Canal, near Nevski Avenue. It had been established in the 1760's by the merchant Philip Jacob Demuth or Demouth (d.1802). Moreover, Demuth acquired a large house at the corner of Nevski and Admiralty Square, where he established another hotel, London, also known as the Hôtel de Londres. It is not far from Morskaya Street (which crosses Nevski at a slightly more southern point), but Pushkin erred in situating it specifically there.

In the draft of Onegin's Journey (V: 3-4) Pushkin's hero "awoke a patriot in the Hôtel de Londres in Morskaya Street (prosnulsya raz on patriotom / v Hôtel de Londres chto na Morskoy). During his trip to Leningrad Vadim Vadimovich puts up at Astoria, a luxurious hotel at the corner of Morskaya ("Herzen") Street and Isaac Square (LATH, 5.2). Further west on the same Northern side of Morskaya Street is the Nabokov house (No. 47). It looks familiar to Vadim Vadimovich who must have visited it as a child:

To be quite honest, only the dogs, the pigeons, the horses, and the very old, very meek cloakroom attendants seemed familiar to me. They, and perhaps the façade of a house on Gertsen Street. I may have gone there to some children's fête ages ago. The floral design running above the row of its upper windows caused an eerie shiver to pass through the root of wings that we all grow at such moments of dream-like recollection. (ibid.)

My father was a gambler and a rake. His society nickname was Demon. Vrubel has portrayed him with his vampire-pale cheeks, his diamond eyes, his
black hair. (2.5)

Demon Seated and Demon Downcast are Vrubel's most famous paintings. They depict Demon, the eponymous hero of a poem by Lermontov. Lermontov's Demon falls in love with the Georgian girl Tamara. On the other hand, Tamara is a character in VN's memoirs Speak, Memory and the title of Vadim's first novel.

Lermontov is the author of The Hero of Our Time (1840), a novel that consists of five novellas. The first of them is entitled Bella ("Бэла"). Charlie Everette (the future Karl Ivanovich Vetrov) calls Vadim's daughter Bel (Isabel), who is soon to elope with him to Soviet Russia, "Bella:"

We had coffee and kirsch in the lounge, and Charlie Everett showed us pictures of the summer Camp for Blind Children (who were spared the sight of its drab locust trees and rings of ashed refuse amidst the riverside burdocks) which he and Bella (Bella!) were supervising. (4.7)

I recognized the critic Basilevski, his sycophants Hristov and Boyarski, my friend Morozov, the novelists Shipogradov and Sokolovski, the honest nonentity Suknovalov, author of the popular social satire Geroy nashey ery ("Hero of Our Era") and two young poets, Lazarev (collection Serenity) and Fartuk (collection Silence). (2.4)

Incidentally, Lermontov translated to Russian ("made a miserable hash of") Wanderers Nachtlied, one of Goethe's most famous poems:

Горные вершины
Спят во тьме ночной;
Тихие долины
Полны свежей мглой;
Не пылит дорога,
Не дрожат листы…
Подожди немного,
Отдохнешь и ты.

Nebo Shillera i Gete (the sky of Schiller and of Goethe) is mentioned in Pushkin's EO (Two: IX: 6). According to "you" (who apologized for the "aphorism"), everything is beautiful na fone neba (against the sky). (LATH, 7.4) Cf. also Nebesnyy, one of the names Vadim tries on striving to remember his surname:

Yes, I definitely felt my family name began with an N and bore an odious resemblance to the surname or pseudonym of a presumably notorious (Notorov? No) Bulgarian, or Babylonian, or, maybe, Betelgeusian writer with whom scatterbrained émigrés from some other galaxy constantly confused me; but whether it was something on the lines of Nebesnyy or Nabedrin or Nablidze (Nablidze? Funny) I simply could not tell. (7.3)

Lermontov's Queen Tamara (the heroine of a 1841 poem Tamara who should not be confused with a character in Demon) is

Прекрасна, как ангел небесный,
Как демон, коварна и зла.
Beautiful, like a heavenly [nebesnyi] angel,

В глубокой теснине Дарьяла,
Где роется Терек во мгле,
Старинная башня стояла,
Чернея на чёрной скале.