Sardinia's main town, Cagliari, was established around 700 BC, and has an impressive old part, called Castello, mainly built of limestone. There are also some Art Deco and Neoclassical buildings in Cagliari. Sassari, the island’s second-biggest town, has a worthwhile archaeological museum and no shortage of beautiful churches, among them the Gothic St. Nicholas Church, which houses a fine collection of art works.