Elementary School King Petar I was founded in 1718, while the building in which school is located today was built in 1905-07. It was projected by Jelisaveta Nacic, the first Serbian female architect, when she was only 27 years old. At the time of the construction, it was the most modern school building for elementary education not only in Belgrade, but in entire Serbia, and is named the "ornament of the school architecture". Exceptionally representative, which was conditioned by the position in such an important street and in the immediate vicinity of the Cathedral Church, the building was the true representative of the social and cultural situation in Serbia at the beginning of the 20th century.
The building was constructed on the sloping ground of the highest part of Sava slope, by the most modern construction procedures, and it consists of a basement, semi-basement, a ground floor and the first floor. The building consists of three tracts, the most important and the most representative of which was set up sidelong, on the corner of the Gracanicka Street and Kralja Petra Street, thus creating in front of it a triangular square. From the backyard side there was a wing set up in the shape of the letter G, which along with the classroom tract makes a small inner courtyard.
The elementary school "King Petar I" is shaped according to all postulates of the academic architecture, with the art nouveau elements, which are reflected in the interior more than on the facades. The facades facing the street are done in three, that is, in two girths, with the dividing wreaths between the floor and with the large roof wreath ending in the attic with balustrade. The representative entrance protruding bay with tall arched windows of the auditorium on the first floor dominates the main facade. On the sides, the dynamics was achieved with the protruding bay highlighted with the triangular sills above the windows on the first floor and some calmly shaped gaps of the ground floor. The yard facades are more modest.