Sennaya Square emerged in 1738–1739 when the authorities decided to lay out the Saar Perspective (now Moskovsky Prospekt), establishing a connection with Moscow. The intersection with Sadovaya Street became Sennaya Square. Initially, it was a vast wasteland but strategically important for organizing trade as the crossing of two main roads leading to Europe and Moscow. This wasteland was adapted for wholesale hay warehouses, hence the name Sennaya Square. The first architectural dominant of the square was the Assumption Church, built with funds from merchants trading at Sennaya. Between 1753 and 1765, a significant late Baroque monument was erected on Sennaya Square — the Assumption Church (Spas na Sennoy).

Under Catherine II, the canals and rivers near Sennaya were reinforced, allowing for denser construction around the square. The Empress allowed free trade on the territory, supporting the formation of a "people’s market" for the poor population, believing it would help combat resellers.

Between 1753 and 1765, a significant late Baroque monument was erected on Sennaya Square — the Assumption Church (Spas na Sennoy). A separate building — the Guardhouse (house No. 37 on Sadovaya Street) — was built in 1818–1820 by architect V. I. Beretti based on a design by architect Luigi Rusca with some modifications. Rusca himself left St. Petersburg for his homeland in April 1818. This is a federal architectural monument.

1774 is considered the unofficial birth year of the Sennoy Market. Initially, the square occupied a vast area stretching to the Fontanka River. By the early 19th century, the square’s territory had shrunk to its current size. In the early 19th century, as part of a large-scale improvement of St. Petersburg, the entire perimeter of Sennaya Square was reconstructed according to a project by Vikentiy Beretti. At that time, the second architectural dominant — the guardhouse — was built to restore the square’s symmetry, disrupted by the church.

In June 1831, a massive spontaneous popular uprising occurred here — the cholera riot, when an enraged crowd staged a pogrom and killings at the cholera hospital. From the mid-19th century, Sennaya began to be mentioned as one of the most dangerous and disreputable places in St. Petersburg, especially the adjoining Vyazemskaya Lavra market (link) and the Malinnik brothel (link). Contemporaries described Sennaya as a "hotbed of evil." City authorities made many attempts to restore order at Sennaya. Along the square were taverns, inns, pubs, shelters, and brothels. The nature of trade also changed since the city limits expanded, and Sennaya was no longer near poor peasant districts; trade from carts was replaced by reselling. Sennaya Square gradually fell into a disgraceful state. After a major fire on its territory, city authorities planned a full or partial reconstruction of the square. However, it was decided to build four market pavilions on its territory.

The first pavilion sold meat, the second fish, the third vegetables and fruits, and the fourth baskets, tubs, brushes, and barrels. The square was covered with a layer of dirt and horse manure, creating a strong stench. Beggars scurried around Sennaya, asking for alms. On holidays, it was difficult to pass through the crowd on the square. Public punishments of fraudsters and thieves were carried out near the guardhouse. Nevertheless, Sennaya was an important part of the city’s trade economy. For example, buildings on the plot between the modern Moskovsky Prospekt, Yefimova Street, and the Fontanka River embankment were called Vyazemskaya Lavra and were among the most terrible slums in the city. The life and morals of the inhabitants of the district around Sennaya were repeatedly described by writers such as Dostoevsky (novel "Crime and Punishment") and Krestovsky (novel "St. Petersburg Slums"). Until the mid-19th century, people caught in robbery, theft, and fraud at Sennaya Square were subjected to public corporal punishments ("trade executions") — described by Nekrasov.

"Yesterday, around six o’clock,

I went to Sennaya;

There they were whipping a woman,

A young peasant woman."

Nikolay Nekrasov in 1848 described a scene of a woman being whipped at Sennaya Square — although whips were officially abolished in 1845, they could be replaced by rods and switches. Public punishments were rare and applied only for serious crimes — theft or murder. In the 18th century, a written permit from the landowner was enough to punish peasants.

By analogy with the "belly of Paris," it is called the "belly of Petersburg." Vsevolod Krestovsky in "St. Petersburg Slums" left a vivid description of this dreadful place — "Along the edges of the square, in huge, multi-story, no less dirty than the street houses, lights flickered in the windows, and lanterns above the entrance doors indicated whole rows of taverns, inns, eateries, snack cellars, wine cellars, pubs, with porter houses and those special shelters where all rejected depravity is molded, hidden, sickened, and dies, from which there is almost no return to a cleaner sphere and where only two outcomes are known — prison and cemetery."

At the end of the 18th century, under Paul I, the first wooden building of the Guardhouse — a military guard and prison — appeared here. By the 1820s, the building was rebuilt in stone, and it was precisely opposite it that public corporal punishments took place — whippings and rods were a common spectacle. Today, this Guardhouse building (house No. 37 on Sadovaya Street) is a separate building on the square, built in 1818–1820 by architect V. I. Beretti based on a design by Luigi Rusca with some modifications. Administrative offenders were also held in this building — among them was Fyodor Dostoevsky, who spent several days here. Rusca himself left St. Petersburg for his homeland in April 1818.

Between 1883 and 1886, the now-lost buildings of the Sennoy Market were built in the center of the square according to the project of architect I. S. Kitner and engineers G. von Pauker and O. E. Krel.

Under Soviet rule, Sennaya was renamed Peace Square and was conceived as a link between the city’s historic center and the new socialist Leningrad. From the 1930s to the 1960s, the square underwent reconstruction and was beautified; the market pavilions were demolished. In 1961, as part of Khrushchev’s anti-religious campaign, the Assumption Church was demolished. On the site of the destroyed church, the vestibule of the metro station was built. The authorities almost immediately recognized the mistake of their decision, proposing a plan to reconstruct the church as early as 1967; fruitless discussions about restoring the temple continued for the following decades. In the second half of the 20th century, Sennaya again began to decline, with fences and construction structures of new metro line vestibules decorating the square for several decades, and several buildings were demolished due to their emergency condition. In the 1990s, after the collapse of the USSR, a chaotic street market appeared on Sennaya’s territory, where impoverished city residents from all over came to sell their valuables to make a living. In fact, the square turned into a street market and one of the most disreputable and dangerous places in the city, as before the revolution.

In 1907, one of the first tram lines passed through Sennaya Square (from 2007 to 2013, traffic was suspended).

In the 1920s, the slums, dens, and pubs surrounding the square were demolished.

In the 1930s, reconstruction was carried out — the buildings of the Sennoy Market were demolished, and the area was asphalted and landscaped.

During the Siege of Leningrad, many buildings on the square were destroyed or damaged.

In 1950, the facades on the northern side of the square received a unified Soviet-style design.

In 1952, Sennaya Square was renamed Peace Square.

In 1961, the Spas-na-Sennoy Cathedral was blown up on the square.

In 1963, an above-ground vestibule of the "Ploshchad Mira" metro station was built on the square. The intercity bus station No. 1 was located at Peace Square.

In 1991, due to the construction of the "Sadovaya" metro station under Peace Square, an underground passage was arranged. In the same year, the square’s original name was restored, and in July 1992, the metro station "Ploshchad Mira" was renamed "Sennaya Ploshchad." A spontaneous market and many trading kiosks reappeared on the square.

In 1999, the canopy of the "Sennaya Ploshchad" metro station pavilion collapsed. Seven people died. (more here https://reveal.world/ru/story/rossiya-avarii-i-tehnogennye-katastrofy/tragediya-na-sennoj)

In 2003, the square was reconstructed; trading pavilions were built, and a chapel was erected in memory of the demolished Assumption Church. At the same time, the Tower of Peace was installed on the square, designed by architect Jean-Michel Wilmotte and sculptor Clara Halter. This tower is a gift from France for the 300th anniversary of St. Petersburg. The tower is a stele with transparent semicircular panels on both sides bearing the word "peace" in 50 languages. Wilmotte and Halter are also the authors of a similar Wall of Peace (Mur pour la Paix) on the Champ de Mars in Paris.

During the anomalous heatwave in summer 2010, the Tower of Peace cracked and was dismantled. Governor Valentina Matviyenko stated that in just seven years, the monument had fallen into disrepair and would not return to the square, as "city authorities are preparing a project to reconstruct the square, aiming to restore its original appearance; numerous trading pavilions will also be dismantled."

Since 2011, there have been plans to restore the blown-up cathedral, but active construction has not begun. Between 2011 and 2013, an above-ground vestibule of the "Spasskaya" station, opened in 2009 but previously without its own exit, was built. In connection with this, in 2011, the trading pavilion in front of the future "Spasskaya" vestibule was dismantled. In September 2016, the final dismantling of trading pavilions on the square began.

Sources:

https://ru.wikipedia.org/wiki/Sennaya_Square_(Saint_Petersburg)

https://sharapov-m.livejournal.com/3614.html

https://dzen.ru/a/ZViUb6Zw2Ae3Oasf