В главном зале работает синхронный перевод.

in

Breakdown of В главном зале работает синхронный перевод.

• работать: to work
• главный: main
• зал: the hall

Questions & Answers about В главном зале работает синхронный перевод.

Why is it в главном зале and not в главный зал?

Because в главном зале expresses location, not motion.

In Russian, в can take:

• the prepositional case for where? → in
• the accusative case for where to? → into

So here:

• в главном зале = in the main hall
• в главный зал = into the main hall

Since the sentence says where the service is operating, Russian uses the prepositional case.

Why is в used here, not на?

Russian usually uses в for being inside an enclosed space, such as a room, hall, building, or city.

So:

• в зале = in the hall

You would normally not say на зале in standard Russian.
The preposition на is used for things like:

• surfaces: на столе = on the table
• some events/places by convention: на концерте, на работе, на вокзале

With зал, the normal choice for physical location is в.

Why does работает mean something like is available here?