Limestone is a sedimentary rock, composed mainly of calcium carbonate, that is formed from the remains of marine organisms such as coral and shells. It has a smooth, granular surface that is often used for walkways and patios. Cobblestone is a natural stone, composed of small, rounded pieces of rock, usually granite or basalt. Cobblestones are usually used in paving projects and can be used to create a variety of patterns and textures. Both limestone and cobblestone are durable and long lasting materials that can be used to enhance any outdoor space.