This is the 14736th most frequent German word.
nächtlichen
"Nightly" or "nocturnal."
In this sentence, 'nächtlichen' is used as an adjective describing 'Geräusche' (noises), specifying that these noises occur during the night.
Die nächtlichen Geräusche im Wald waren unheimlich.
The nocturnal noises in the forest were eerie.
Here, 'nächtlichen' is an attributive adjective modifying the noun 'Spaziergänge' (walks), indicating that the walks happen at night.
Nächtlichen Spaziergänge können sehr entspannend sein.
Nightly walks can be very relaxing.
In this example, 'nächtlichen' describes 'Temperaturen' (temperatures), providing the additional information that these temperatures are measured or observed during nighttime.