。
The air in the forest tastes wonderful.
Literal
Forest [attributive-の] air [topic-は] is-delicious.
A simple but instructive sentence. おいしい is normally used for food that tastes good, but Japanese extends it metaphorically to describe air and water that are refreshing or pleasant to breathe — a nice semantic broadening English handles with a different word ('fresh,' 'crisp'). 森林 is the kango compound for 'forest, woodland' (contrasts with native 森).