Bauen aud fremdem Boden. Eigentumserwerb durch den gutgläubigen Besitzer

The aim of this paper is to present the development of the legal concept of good faith in European legal tradition by means of claim in case of building on someone else’s land – art. 231 § 1 of Polish Civil Code. This claim pretends to be an exception to the superficies solo cedit – rule, offering some possibility to avoid its strict results. The paper takes particularly Polish and Austrian regulations into consideration. The author describes the history of meaning of good faith from roman law until today. He indicates the Germanic origins of the claim from art. 231 § 1 and the influences of Austrian Civil Code (ABGB) § 418. The paper contains a review of statements of doctrine and Polish Supreme Court in 20th century. The described example is also a model of application of historic-comparative method in legal sciences.