The Kiennese Plain (Hulstrian: Kiener Flachland) is the name of a high plain in the Northern Schnee-Berge Mountains that forms the urban heart of the Crownland of Hulstria in Hulstria. Surrounded by the snow-capped tops of the Schnee-Berge mountains, the broad, glacial valley formed a well-defended and fertile base for settlement that became the centre of the Hulstrian Empire. Its defensible base made it ideal for establishment of the Hulstrian capital there during the Hulstrian Rebellion. It was found by Erich Kien, a fur trapper in the employ of the Lord of New Liore, in 1510.
The Kiennese Plain is cut through by the river Phönix, a tributary to the river Buden which gives its name to the city of Phönix, which sits at the narrow northeastern end of the plain. The eponymous city of Kien dominates the centre of the valley. The Kiennese plain, with the exception of a more hilly section that separates Kien from Phönix, has become highly urbanised to the extent that it is now considered to be one single large conglomeration.