This is the 15888th most frequent Turkish word.
tünelinde
"In its tunnel."
Here, 'tünelinde' indicates a location (in the tunnel).
Arabamız bozuk tünelinde kaldı.
Our car broke down in the tunnel.
In this sentence, 'tünelinde' describes where the action of walking took place.
Tünelinde yürürken havanın soğuk olduğunu fark ettik.
While walking in the tunnel, we noticed that the air was cold.
Here, 'tünelinde' specifies possession (referring to the mountain's tunnel).