Learn Russian: Когда мы вошли в зал, там было тихо. - When we entered the hall, it was quiet there.

вошли is the past tense plural of войти (to enter). It is formed by adding the prefix во-, which is a spelling variation of в- meaning into, to the verb идти (to go on foot). It is perfective, meaning the action of entering was fully completed before the second part of the sentence took place.

Why do we have the preposition в right after a verb that already has the в- prefix?

This is a common pattern in Russian! When using prefixed verbs of motion, you often repeat the preposition. To say you enter a place, you use войти followed by the preposition в and the Accusative case for your destination. Because зал is a masculine inanimate noun, its Accusative form looks exactly like its dictionary form.

Why is the verb было in the neuter form?

When describing a general atmosphere or environment, Russian uses an impersonal sentence, meaning there is no specific subject like he or it doing the action. In the past tense, these impersonal structures always use the neuter verb было followed by a state adverb like тихо.

Could we use the imperfective verb входили instead of вошли?

Using the imperfective входили would mean you were in the ongoing process of walking through the doors, translating to while we were entering. By using the perfective вошли, you emphasize that you completely finished crossing the threshold and only then noticed how quiet it was inside.