Living room in every home generally has the largest volume. The simple cause of this is a living room is regarded as a "gateway" to all other internal spaces. But in case of an apartment block in crowded city, scarcity of space is an issue resulting in compact architectural planning. Thus giving rise to apartments with bare minimum spaces. There is one vitally important thumb rule with regards to playing with internal spaces. The more light you may allow to enter a room, the more it will be perceived as a big room in terms of volume is concerned. Also if you use brighter color shades that will help a uniform and smooth reflection of light equally in all the corners of the living room, it will be easier and effortless transition from small to big room perception.