This is the 11470th most frequent Polish word.
jaskinie
Caves.
In this sentence, 'jaskinie' is used as the main subject, denoting a geographical feature (plural form) visited by tourists.
Jaskinie są często odwiedzane przez turystów.
Caves are often visited by tourists.
Here, 'jaskinie' is the direct object of the action 'zwiedzaliśmy' (we explored), describing a location explored.
Wczoraj zwiedzaliśmy piękne jaskinie w górach.
Yesterday, we explored beautiful caves in the mountains.
'Jaskinie' serves as the subject, whose attribute (being difficult to access) is discussed.