This is the 9197th most frequent Polish word.
tajemnice
"Secrets" or "mysteries."
In this sentence, 'tajemnice' refers to mysteries or secrets hidden in the context of the old castle.
Dziecko odkryło tajemnice starego zamku.
The child discovered the secrets of the old castle.
Here, 'tajemnice' points towards confidential information regarding a project, emphasizing their concealed nature.
Po latach ujawniono wszystkie tajemnice związane z projektem.
After years, all secrets related to the project were revealed.
In this usage, 'tajemnice' conveys a single or multiple pieces of private or confidential matters that require keeping.