From 1881, ten years after the death of Boğos Düzyan, the building housed the Club de Spor Oriental (later Cercle d’Orient, and today Büyük Kulüp), a club for diplomats serving in Istanbul and high ranking Ottoman officials. From 1883 to the 1890’s, the Greek Consulate operated from this building. According to commercial ledgers from 1898 and 1901, its street-front shops were operated by one İlyas the Butcher and one Muhallebici (Pudding maker) Ahmet Efendi. In 1901, as the Cadde-i Kebir (“The Grand Avenue” now İstiklal Street) was being expanded, the Düzoğlu mansion underwent major changes along with all the other buildings on the avenue. During this period of renovation between 1898–1902, a quarter of the building was demolished, floor levels were added, and the building was expanded on the garden side. During these last additions, a new stairway was built onto the back of the building. The current form of the building as a brick structure of five floors dates back to these years. The marks left by the renovation can still be seen in the fabric of the walls today: timber beams that once rested on the part of the brick wall perpendicular to İstiklal Street have left their marks and were most likely part of the first Düzyan mansion. The later additions from around 1900 are distinguished by their larger and regular industrial bricking.
The Cadde-i Kebir was originally only about five meters across, but attained more or less its current width with these renovations. In documents dated 1904–1905, the Düzoğlu mansion can be seen to be aligned with the other buildings on the avenue. As part of the reinforcements and to increase height, iron I-beams and brick courses, also known as “French vaults”, were added in place of timber beams. As the building grew to five floors, structural reinforcement became necessary. Traces of these improvements can be seen in the sections reinforced with a secondary vault or arch, and the monolithic marble columns installed in the lower floor.
Following the large scale architectural changes of around 1900, the mansion, still owned by the Düzoğlu family, assumed a new function more appropriate to the socio-cultural developments of the last years of the Ottoman Empire. This multi-storied, modern mansion evolved into a commercial Beyoğlu han as it housed the American sewing machine manufacturer, the Singer Corporation. In a postcard dated 1908 depicting the Second Constitution celebrations, the American flag can be seen hanging from the bay window of the Singer Corporation building. This postcard reveals just how dramatically the Cadde-i Kebir had changed over the previous century. Gone were the two-to-three storey traditional Ottoman buildings strung along a narrow street; instead multi-storied hans and apartment blocks lined a broad avenue. The ‘Singer Han’, with its new façade and function, reflected the characteristic features of commercial Levantine structures at the beginning of the 20th century. Alongside elements reflecting an Ottoman architectural legacy, the building also reflects an austere and distinctive classicism quite different from the Eurocentric understanding of the concept. The distinctive features of the façade include a series of semi-circular arches, cast iron colonettes adorning the bay windows and recessed windows that reveal the width of the walls. Also, the clustering of windows on the top and ground floors in subsequent years has resulted in a more modern design.
Despite the tense relations between the Young Turk government of the period and the Singer Corporation, the company kept operating from this building during the period of the Republic. When it was bought by the late Vehbi Koç in 1960, a new era began for the building now known as the “Merkez Han”. The Merkez Han was the first building bought in the 1960’s following Vehbi Koç’s decision to transfer his commercial activities from Ankara to Istanbul.
In 1961 one of the first Koç Group companies, Gazsan Likid Gaz Ticaret ve Sanayi A.Ş., began to use the building. In the words of Can Kıraç, former chief of the executive committe of Koç Holding, it was “in a run-down state by then”. After housing a succession of other companies, in 2005 the decision was taken to convert the Merkez Han into a research center for Koç University. The building underwent modernization, with special attention given to the preservation of the historical structure dating from the early 20th century. As of that year, the Merkez Han began to host scholarly activities, while the structural reinforcement and remodeling continued. In 2008, the work undertaken by the VKV Projects and Construction Coordination Office was found worthy of the “Chamber of Architects” 11th National Building Achievement Award. Structural adjustments continued until the building’s official inauguration in 2012.
This history of the Merkez Han is based on the research of Paolo Girardelli, Assoc. Prof. at Boğaziçi University.