This is the 1513th most frequent Polish word.
wielki
"Great" or "big."
Here, 'wielki' is used as an adjective to emphasize the large and expansive nature of the forest.
Wielki las rozpościerał się przed nami.
A vast forest stretched out before us.
In this context, 'wielki' is utilized metaphorically to describe the importance and significance of the day.
To był wielki dzień w moim życiu.
It was a great day in my life.
'Wielki' is descriptive here, referring to the mountain's physical size.