The administrative building of Rapla KEK, with the current name Okta Centrum, was designed by architect Toomas Rein and completed in 1977. In the same year, Aulo Padar received an annual award for its interior design. The building with the total area of 3,076 m2 and two above-ground floors is located in Rapla in the area between Mahlamäe and KEK residential district. In 2015, the octagonal Okta Centrum was declared a cultural monument as an Estonian Soviet-era collective farm building. In 2021, the Estonian Association of Architects included it in the list of the ten most prominent objects of architecture of the 20th century.
In the centre of the building there is a gym with a skylight, surrounded by a corridor. The central part of the façade features a row of strip windows, behind which are the offices on the second floor.
In the central part of the first floor there are the lobby and shopping premises with corridors running along the sides of the building. The corridors open to smaller ancillary rooms: a sauna and a changing room with the contemporary décor. There is a café with secondary rooms at the back side of the building. The access to the courtyard pool is also located there.