particles - Usage of か after a clause?

Here's a sentence I found:

デパートはどこにあるか、知っていますか？
Do you know where the department store is?

What's the purpose of the か particle in 「どこにあるか」? Under what circumstances do I use it?

I'm fairly sure it's not the か that's normally used to form questions, like the second か in that sentence, nor is it the か that means “or.”