Having started on April 04, 2018, excavation works have been completed on November 25, 2019, at the Mandarin Oriental Bosphorus Hotel Project, which is the deepest and largest construction pit along the shoreline of the Bosphorus. The depth of the excavation, which is totally under the sea, is 24.50 m at the shoreline of the Bosphorus and 31.50 m next to the Muallim Naci Street. A special hybrid shoring system, consisting of top-down and bottom up systems supported by steel struts, has been selected and applied for a safe excavation, which is very close to the sea, without damaging surrounding roads and buildings. Within the scope of the project; 21,600 m2 of 100 cm thick diaphragm wall with a depth of 35 to 60 m; 10,900 m of foundation pile and 10,100 m of top-down pile have been installed. Besides, at the street side of the working area; 4,600 m of high capacity single bore multiple anchors (SBMA) have been executed by Kasktaş. The construction works have been commenced by the “Top and Down Construction System” which enables excavation works and construction of the building upwards at the same time, simultaneously. Within the scope of the project, a total of 6 no. pile tests have been executed and the safety of the construction pit and the shoring system has been observed regularly with various instrumental monitoring techniques, such as inclinometers, settlement plates, coordinate check points, tiltmeters and strain gauges, from the commencement of the excavation works till the completion of the excavation works.