Learn Polish: Jakie imponujące widowisko! - What an impressive spectacle!

We use jakie because it modifies a noun phrase (imponujące widowisko). Words like jaki (what a) and taki (such a) act like adjectives and must agree with the noun's gender and case. If you were modifying an adjective on its own, an adverb, or a verb (for example, "How impressively they played!"), you would use jak.

What gender and case is this phrase in?

It is in the nominative case (the dictionary form used for subjects and simple exclamations) and it is neuter. Widowisko (spectacle) is a neuter noun, so both the exclamatory word (jakie) and the adjective (imponujące) must take neuter singular endings.

The word imponujące looks a bit like a verb. Where does it come from?

It comes from the verb imponować (to impress). By taking the verb stem and adding -ący/ąca/ące, Polish creates an active participle—a word that acts like an adjective describing what something is doing. So imponujące literally means "impressing," which we translate as "impressive." It takes the -e ending here to match the neuter noun widowisko.

Could I say Co za imponujące widowisko! instead?