The vestibule of the Otwock Wielki Palace was initially a representative hall into which the double external staircase led directly from the courtyard. It is one of the 4 rooms of the palace with original decoration.
The semi circular niches supported by richly decorated corbels are the main features. The original Baroque sculptures that filled the niches were destroyed between 1809 and 1828. Present statues depicting mythological deities were executed in 1975 by Stanisław Kulon.
The decoration of the vestibule was to resemble an antique grotto and a Palladian Corinthian hall. The walls were covered with a mixture of sand, lime, green glass and granite. The southern wall is filled with a wide semi circular entry into the ballroom framed with stucco decoration in the form a fabric supported by 4 putti and two herms in the form of a semi nude female and male. The herms indicated the initial division of the palace's structure into the wife and husband's space and bears strong resemblance to the current owners Ludwika Maria Bielińska and her husband Kazimierz Ludwik.
Between 1787 and 1790, Franciszek Bieliński, the palace's owner, has visited Italy several times. During his sojourn in Naples he acquired a collection of 85 teraccotta busts and copies of antique sculptures from the collection of la Maison Farnese and originating from the Pompei and Herculanum excavations. As the collection was intended to be housed in Otwock Wielki, the palace underwent some structural changes inside.