While other towns in Norway have suffered with the decline of this industry, Stavanger has kept its economy booming by diversifying, first into shipbuilding and now into oil. These two contrasting industries have created a city of two halves – a modern area of high-rise buildings and a historic centre with cobbled streets and old wooden houses. The city centre was the birthplace of Alexander Kielland, one of the great 19th-century Norwegian novelists. Stavanger Cathedral, dating from 1125, is an impressive building and the only medieval cathedral in Norway that has not been substantially altered since it was first built. From Stavanger you can explore the attractive blue waters of Lysefjord, surrounded by cliffs and striking rock formations, and also visit Hafrsfjord where the Viking King Harald won an important battle that started the Unification of Norway. Those preferring to explore on their own may wish to visit the interesting Petroleum Museum.