Just north of the city centre, Østerbro is an upper middle-class district with a number of fine mansions, some now serving as embassies. The district stretches from Nørrebro to the waterfront where ''The Little Mermaid'' statue can be seen from the promenade known as Langelinie. Inspired by Hans Christian Andersen's fairy tale, it was created by Edvard Eriksen and unveiled in 1913. Not far from the Little Mermaid, the old Citadel (''Kastellet'') can be seen. Built by Christian IV, it is one of northern Europe's best preserved fortifications. There is also a windmill in the area. The large Gefion Fountain (''Gefionspringvandet'') designed by Anders Bundgaard and completed in 1908 stands close to the southeast corner of Kastellet. Its figures illustrate a Nordic legend.