The decision to rebuild the Royal Castle in Warsaw entailed a number of activities beyond srticte construction work. An opportunity was seen to conduct thorough scientific research, of an object that until then had been inaccessible to architectural researchers or archaeologists. Paradoxically, the complete destruction of the Castle became the only and unique opportunity to undertake this type of field research. The article, summarizes the activities undertaken in the research field before and during the restoration of the Royal Castle with an emphasis on presenting the complexity and difficulties of the research process. The study covers various aspects, from decision-making through the implementation of research tasks to the complexity of methodological issues. The most important discoveries resulting in the creation of theories about the origins of Warsaw Castle and Warsaw itself are presented. This was the period in which the so-called modern archaeology was born, and the research at the Warsaw castle can be considered pioneering. It should be noted that the presented study does not exhaust the entire subject. It is only an attempt to summarize the work that was undertaken in a social act to save cultural heritage, and to show how heroic and admirable was the work of a committed scientific community.