Limestone is a very common type of sedimentary rock, and is the surrounding structural rock of most cave systems. Limestone is easily permeated and eroded by water, so limestone structures are often seen in karst landscapes, areas where the visible rock has been worn away and eroded, resulting in interesting holes and cliff-faces (Wikipedia). Throughout history, limestone has been a major part of industrial production and construction, as it is easily mined and crushed to create various products. Limestone is often composed partly or entirely from fossilized animal remains, and fossils are often found intact in lime deposits.
Because of the ease of mining and shaping limestone, it has been used in buildings throughout history. The Pyramids in Egypt are largely composed of limestone. Despite its permeability, limestone structures are resistant to weather, creating structures that remain standing despite their age. Many historical structures in the Americas, Europe, and Asia are built partly or entirely from limestone. Cheap limestone products are also found in dozens of commercial applications, from road aggregate to toothpaste, and a food-safe version is often used to add calcium to food.
Limestone is a type of sedimentary rock usualy found in hills, outcrops, islands and caves etc.
It has various uses as a building material, in road construction, as a pigment and coloration, to paint/daub trees and plants (as quicklime), in paints and toothpastes, medicines, cosmetics and other preparations etc.
In building/architecture it has been widely used since earliest times-- the Great Pyramid at Giza, Egypt for one, as well as many famous buildings in the UK, and other parts. Apart from limestone blocks used in construction, there is also limestone/Portland cement from limestone, as mortar and so on.