When Ernst Ziller, the German architect, was assigned the building of the Crown Prince’s Palace, it was on condition that the building would neither be majestic nor modelled on other European Palaces. The building was to harmonize with the homes of the wealthy Greeks of that time and be representative of the ruling social class of the country. It appears that those guide-lines were laid down by George I.

The result is a three-storey neo-classical building with a plain symmetrical facade. The main part of the building is flanked by two slightly protruding wings. On the second floor there is a row of double windows separated with spaces and carved with heraldic symbols, representations of the four seasons, the letters K and Σ (for the Greek spelling of Constantine and Sophia) as well as characters from Greek mythology. At the top of the building Ziller had statues placed. All sides of the building are unpretentious. The only protrusion is the porch with its Ionic columns at the main entrance on Herodon Attikou Street.

When designing the facade and the floor plan of the Crown Princes’ Palace, Ziller was influenced by the work of his friend and fellow-architect, T. Hansen.

The modifications made to the building from the time of its construction up to the present day are not especially significant. One exception to this is the addition, in 1909, of a ballroom (currently the Credentials’ Lounge) and the extension added to the rear wing (now the Reception Hall) at the beginning of the 1960’s.

The floor plan presents some changes in relation to the original plans of the mansion, which is natural since the building is already a century old. The most important of these are the addition of a second staircase at the rear of the building, which allows communication between the floors without using the central staircase, and the installation of a lift.

The most significant exterior change is the creation of a second large marble staircase during the Presidency of Constantinos Tsatsos, which connects the building with the garden.