Learn Turkish: İkinci köprünün temeli ne zaman atıldı? - When was the foundation of the second bridge laid?

The verb root is at-, which normally means "to throw". To make it passive, we add the suffix -ıl, creating atıl- (to be thrown / to be laid). Finally, we add the definite past tense suffix -dı, giving us atıldı (was laid).

Doesn't the verb atmak usually mean "to throw"? Why is it translated as "laid" here?

You are exactly right! By itself, atmak means "to throw." However, Turkish uses specific phrases for certain actions. The phrase for "to lay a foundation" is temel atmak (literally, "to throw a foundation"). In the passive voice, this naturally becomes temel atılmak (the foundation to be laid).

Why do we use köprünün temeli instead of just köprü temeli?

This is a specific, definite relationship. We are talking about the foundation of a specific bridge (the second one). Because of this, we need the full genitive-possessive structure: köprü-nün (the bridge's) temel-i (its foundation). If we were talking about the general concept of a bridge foundation without a specific bridge in mind, it would be the indefinite noun compound köprü temeli.

Could we put ne zaman at the very beginning of the sentence?