Der Hahn is a very unique restaurant in Idstein. It is located ON a farm, therefore beware of the smell when seated outside ;) It is part of the Gassenbacher Hof/Domaene and solely uses its produce. Products are all local and organic. Downside: the Hahn has weird business hours. And do not expect a wide variety. There are only a dozen dishes. After lunch have a look in the market hall. Especially the meat and cheese is great!