Does a factory count? If so… https://en.m.wikipedia.org/wiki/Boeing_Everett_Factory
Boeing Everett Factory
checks
Volume: 13.3 million m³
That being said, I don’t know if it is internally divided.
There’s a really large cave in Southeast Asia somewhere.
kagis
The Sơn Đoòng cave in Vietnam:
Formed in Carboniferous/Permian limestone, the main Sơn Đoòng cave passage is the largest known cave passage in the world by volume – 3.84×10⁷ m³ (1.36×10⁹ cu ft), according to BCRA expedition leader Howard Limbert. It is more than 5 kilometres (3.1 mi) long, 200 metres (660 ft) high and 150 metres (490 ft) wide.
So that’d be nearly triple the volume of the Everett Factory. Though the cave has two holes in its roof, and I don’t know exactly how you define “room” here.
They had to change their venting and airflow system for that building after it formed a cloud and rained inside. When your room can have weather systems, I feel you’ve entered a whole new category of ‘room’ by definition.
Thats crazy! Fascinating! Could one engineer a climate system such that it always rained? Can lightning and thunder occur as well?
Interesting question. Are we talking about the volume or the floor area? For volume maybe a church? Then St. Peter’s Basilica in Vatican City would be the largest. I don’t know the layout though, but I assume a large portion of it is the main “room”.
Or do stadium with a roof count? Then maybe one of these?
Edit: I don’t think I really thought this through. I was thinking too much of more roomy rooms. Most convention centers probably have larger exhibition halls.
Probably volume altho i suppose I’m probably taking it for granted that a volumetrically massive room would also have massive floor space
Stadium with a roof doesnt count