In an open-plan room, a single large rug acts like a visual island, quietly telling you, “This part is the living area” or “This is where we sit and talk.” By placing a rug under the sofa, coffee table and chairs, you anchor those pieces together and separate them from, say, the dining table behind.
It doesn’t have to cover the whole floor. Ideally, at least the front legs of major furniture sit on the rug. That makes the arrangement feel intentional and contained, rather than pieces floating randomly in a big empty space.
The rug also helps with acoustics, softening sound in what can otherwise be an echoey room with hard surfaces. Colour and pattern add personality; you can go bolder on the rug and keep furniture simpler, or the other way round.
Even in a modest home, one correctly sized rug can do a lot of “zoning” work without building a single wall.