Someone made this 3D map of Britannia in U6. One of my gaming dreams is to walk around Ultima VI in first-person and experience the game that way, and in VR. So I was curious to extract the map data from the game but lacked the programming knowledge, and I found this. I never figured out how to open this overworld model (Level_0.x) for me to use as reference. Something about DirectX.
Check out his site, as it has many cool and technical resources for Ultima Vi.
Here's the original fb UDIC post.