Once, Mertens House transformed from a small two-story building into a luxurious mansion, standing out among the historical architecture of St. Petersburg with its unusual design. The architects managed to combine two different architectural styles in its layout and decoration: northern modernism with monumental facade decorations and the geometric-symmetrical style of the Italian Renaissance. Adorned with plant ornaments and three tall arched display windows, this building has served as a trading house for over three hundred years.

St. Petersburg and the neighboring regions have always been at the forefront of architectural fashion, so many of its iconic buildings combine various European directions. In the 18th century, when the history of Mertens House began, Nevsky Prospect was actively being developed with stone mansions, known as 'exemplary.' These buildings, designed during the Peter the Great era, were based on a Western European style with a solid facade.

According to Bogdanov-Ruban's description, such development was driven by Peter I's desire to give the new city beauty. The solid facade proved to be an effective innovation for Russian urban planning, especially in windy St. Petersburg.

The Mertens Trading House, located at 21 Nevsky Prospect, was one of these exemplary buildings. On its site stood a modest two-story merchant's mansion, which changed hands over the century. In 1847, it belonged to Duke Maximilian of Leuchtenberg, son-in-law of Nicholas I. Under him, the building was reconstructed into a four-story apartment house with luxurious apartments and shops, becoming a gem of St. Petersburg.

In the 1870s, the building changed owners again and became known by the surname of a wealthy furrier family. Their main office and shop attracted the fashionistas of St. Petersburg. However, not all of the building was allocated for fur trading. Inside were other shops and offices, such as the confectionery 'Georges Borman,' a branch of the insurance company 'Equitable,' K. Keller's pharmacy, and others.

The confectionery 'Georges Borman' produced Easter chocolate eggs with gifts inside, reminiscent of Fabergé eggs. Later, when the firm became the 'Red October' factory, this product had to be discontinued.

L.F. Mertens believed that there is no limit to perfection, and at the beginning of the 20th century, he planned another reconstruction. The building already attracted attention, but he wanted to turn it into a unique architectural masterpiece. The result exceeded expectations, and the building became famous for its elegance. Its photographs were circulated in guidebooks and art albums.

Mertens entrusted the transformation to architect Marian Lyalevich, who was passionate about the Italian Renaissance. Lyalevich used ideas from Andrea Palladio to decorate the facade with arches on all four floors. This was an innovative solution that required a revision of construction principles. Lyalevich applied a reinforced concrete frame, preserving brickwork where possible. Mertens House is considered one of the oldest buildings despite the reconstruction.

The central part of the facade was adorned with massive letters bearing the owner's surname. Plant ornaments and sculptures by V.V. Kuznetsov emphasize the strict geometry of the building without overloading the facade.

The reconstruction was completed in 1912 and became the main topic of discussion. The house on Nevsky Prospect and the neo-Renaissance style were discussed by both ordinary people and architects. The project laid the foundation for the era of constructivism, when the combination of concrete and glass became fashionable.

Since then, a new wave of demand for Mertens fur products began, and the brand became known beyond Russia. The inscription 'Mertens House' on the facade served as a marketing move and also gave rise to an urban legend that it helped cab drivers deliver the owner home after banquets.

After the 1917 revolution, the Bolsheviks closed the fur business, and the building was occupied by Soviet institutions. In 1944, after the blockade of Leningrad, the Leningrad House of Fashion opened here.

In 2008, the building was restored according to Lyalevich's project. The facade regained its former freshness and chic, complementing other architectural masterpieces on Nevsky Prospect. Inside, there are clothing and shoe stores, as well as an academic service registered to supply gowns and caps.

The merchant family immortalized their name with this remarkable structure, which is considered a masterpiece of St. Petersburg architecture.