Decorative rock is simply a 3-4″ layer of rock covering the ground and filling an open space. If it is designed well, it can seamlessly blend into the landscape and look like it is supposed to be there. Decorative rock is a great way to cover dry shade areas where grass will not grow but with too many tree roots that would destroy a concrete patio. This is a great way to get rid of mud and dog traffic related problems. Many different decorative gravels are available.