On the territory of the Summer Garden, on the site of the current Coffee House, there used to be a pavilion called the "Grotto," which was being built from 1714 according to the idea of Tsar Peter, based on the project (partially rejected by the tsar) of the French architect J.-B. Le Blond, the plans of A. Schlüter and Mattarnovi, and into which, over time, the statue of the Tauric Venus was moved. The construction was only completed in 1725–1727, after the death of Tsar Peter, according to the project of architect M. G. Zemtsov "in a transitional style, foreshadowing the rocaille of the Elizabethan period." Inside, the grotto was decorated with tuff, real sea shells, and "broken glass." In the center was a fountain featuring the god of the seas Neptune on a gilded chariot, surrounded by four hippocamps. The statues, made of lead, were gilded. There was also a musical instrument here — an organ powered by water when the garden fountains were activated. 

Unfortunately, the flood of 1777 completely destroyed the fountain system of the Summer Garden, along with the "Grotto."

In 1801, the "Grotto" was partially dismantled by order of Paul I. Instead of the old building, Paul I intended to erect a garden pavilion that would suit the tastes of the time; the project for the new structure was made by Demertsoff. Work began, but the emperor’s death prevented its completion. Alexander I, who succeeded Paul, ordered the restoration of the building, but there were not enough drawings and plans for this. On April 9, 1826, it was finally decided to rebuild the half-ruined structure. The original project by L. I. Charlemagne was not approved, and the commission passed to K. I. Rossi, who built the Coffee House using the foundation and walls of the previous structure.

A quarter of a century later, during the construction of the pavilion "Coffee House," built on the site of the grotto, Carlo Rossi used the walls of the old Schlüter building but destroyed the dome over the central part and the lavish Baroque decoration of the facades. Sculptural masks on the pylons, garlands, and wreaths on the attic, as well as the stucco frieze, were created by the sculptor V. I. Demut-Malinovsky.

The walls of the hall are finished with a frieze featuring a plant ornament and a smooth cornice. In the Coffee House, the Italian Piazzi opened a confectionery that operated for 30 years. In 1925, during repair work, underground tunnels were discovered beneath the Coffee House. K. I. Rossi preserved the walls of Zemtsov’s Grotto, which had been damaged during the 1777 flood, but destroyed the dome over the central part and the lavish Baroque decoration of the facades.

According to restorers who worked on the monument: probing showed that the walls of Zemtsov’s Grotto have indeed partially survived to this day, as well as traces of the 1721 tuff decoration. The foundations have also been preserved. Even the brick flooring of the Grotto, buried under construction debris at one time, has survived. Unfortunately, it remains hidden by the restorers, and now we cannot see it on the monument.

The Coffee House is a small elegant pavilion in the classical style, rightfully considered one of the best adornments of the famous Summer Garden. Once, on its site stood the grotto built according to the project of architect A. Schlüter. The grotto was a true work of art, its walls decorated with sea shells and columns, and in the middle was a fountain with a statue of Neptune. According to contemporary accounts, one of the grotto’s halls housed a wonderful organ powered by water streams. Unfortunately, the flood of 1777 completely destroyed the Summer Garden’s fountain system, along with the grotto. In 1826, under the direction of architect Rossi, the Coffee House was erected on the site of the grotto in its current form. Rossi preserved the foundation and walls of the grotto, creating a pavilion in the style of classical Russian garden and park architecture. Decorative sculptural images enliven the strict forms of the walls; masks, garlands, and wreaths, as well as rich stucco, give the building a festive and grand appearance.

The decorative elements are attributed to the artist V. I. Demut-Malinovsky. The interior of the house is quite modest: two small bright halls, one of which has windows overlooking the Fontanka River, plant ornamentation on the walls, and smooth cornices. Since the construction of this garden pavilion in 1826, the Summer Garden has had this as one of its liveliest spots. For thirty years, the pavilion housed the confectionery of the Italian Piazzi, attracting lovers of coffee and pastries. Later, it became a very popular restaurant among the city’s public. Perhaps the photo was taken early in the morning, and the restaurant was not yet open. Or maybe the effects of the world war were already being felt. Another curious fact: in 1925, during repair work, builders discovered a whole system of branched tunnels under the pavilion, the purpose of which remains a mystery to this day.

The name "Coffee House" recalls those distant times when one enterprising Italian opened a coffee shop here. Coffee is no longer served here (for that, people usually go to the Tea House located nearby), but the interiors of the Coffee Pavilion are very often decorated with works by contemporary urban artists, since this architectural monument is under the jurisdiction of the Russian Museum. Paintings, applied arts, small sculptures, glass and ceramic items are exhibited here, many of which visitors can purchase on site. Albums and literature on art and painting, various souvenirs — all of this can be bought at exhibitions and sales in the miniature and very cozy Coffee House.

Source:

http://www.peterburg.biz/kofeynyiy-domik-letnego-sada.html#ixzz8eKdxjwnA

https://ru.m.wikipedia.org/w/index.php?title=Кофейный_домик

https://spacefor.ru/sad/grot-v-letnem-sadu