Learn Spanish (Latin America): ¿Dónde hay un baño limpio?

In this sentence, we are looking for any clean bathroom, not a specific one. Because we use the word un (a), we use hay (is there) to ask if one exists. If we were looking for a specific bathroom, like the bathroom (el baño), we would use está: ¿Dónde está el baño? (Where is the bathroom?).

Could I say ¿Dónde está un baño limpio? to mean the exact same thing?

No, that would sound unnatural in Spanish. The verb estar (where está comes from) is used to locate specific things. Since un baño limpio (a clean bathroom) is unspecific, you must use hay. A good rule of thumb: use hay with un/una (a/an), and está/están with el/la/los/las (the).

Why does the word limpio come after baño?

In Spanish, adjectives (describing words) almost always come after the noun (the person, place, or thing they describe). So instead of saying 'a clean bathroom', you say 'a bathroom clean' (un baño limpio).

Why does dónde have an accent mark over the 'o'?

In Spanish, question words like dónde (where), qué (what), and cómo (how) always take a written accent mark when they are used to ask a question. This doesn't change how the word is pronounced, but it tells you immediately that a question is being asked.