[3] From the form of its body to its roof, the concrete structure is reminiscent of the architecture of its Lapau Kajang predecessor, but updated.

It is a one-story, rectangular, concrete structure with a straightforward external and interior design that resembles an extended cottage.

The building's back patio and entryway with its flat roof were still there, but concrete walls had been constructed to enclose the area.

The original back patio of the PSB was converted into a segway leading to the main building in the late 1980s, marking the start of expansion and refurbishment operations.

The structure has five semi-circle arch windows on each side, which were initially open for ventilation, in observance of the Lapau Kajang design.

Entering this space offers a glimpse into the building's history even if the verandahs on both wings are now closed up and part of the exhibition area.

A replica of the Pataratna, the ceremonial dais used for Sultan's coronation and other important rituals, such as the announcement of the 1959 Brunei Constitution, is located in the rear of the space.