private viewing; private showing; sneak preview
An event held before the official opening, such as for a new store, exhibition, or facility, where invited guests can preview the space.
I was invited to the private viewing of the new store.
inspection of a newly completed home
Specifically refers to an inspection event for a newly built house or condominium before the buyer moves in.
マンションの内覧会で部屋の隅々までチェックした。
At the condominium inspection, I checked every corner of the room.