one building (hall, temple, shrine, room)
same room; same place; same building
関係者が一堂に会して議論を交わした。
The stakeholders gathered together and exchanged discussions.
全校生徒が一堂に集められた。
All the students in the school were assembled together.
専門家たちが一堂に集う機会は珍しい。
It is rare for experts to come together in one place.