Porsgrunn marble originates from the area around the town of Porsgrunn in Southeast Norway and has also been used for several large Danish buildings such as the Danish National Bank, Søllerød City Hall and Rødovre City Hall, all designed by Arne Jacobsen. A characteristic element of Porsgrunn marble is the often-large amount of coral fossils which makes the top “alive”. Often shown corals are Halysites, Heliolites and parts of Crinoids. These discoveries in the marble indicate that the sediments are approximately 425 million years old.