I've spent a lot of time at Nautilus working with VR, specifically the Oculus/Meta Quest, Quest 2 and more recently Quest 3 headsets. The work's mostly been targeted at the MoD, for use in mission planning and rehearsal. VR allows people to get a good awareness of the layout of an area before they actually go there, more so than they can with photos or blueprints alone. I've created a number of real-world sites as locations users can explore in VR, both with analogue stick movement and teleporting. Functionality I've added includes opening/closing of doors and windows, a night vision goggles view, a compass, a map that shows the user's live location and orientation and LAN multiplayer, allowing multiple users to explore the same scene together using different headsets.
More recently, I've experimented with mixed reality, specifically an app to view interactive 3D maps generated (ideally) from photogrammetry. Users can move and rotate the map, place MGRS markers and draw routes on it, while still being able to see their real-life surroundings and colleagues. This can replace makeshift 'sandpit' representations of areas used for military planning and briefing.