I spent the last couple of days on and off trying to find a solution for opening/exporting/importing Quake (1) maps. Some software, such as AC3D only support Quake 3 files, so that didn’t work for me. What did work, though, was Blender in combination with andyp123’s Quake 1 BSP Importer for Blender. Instead of the map file it’s enough to supply a bsp, so even if it’s not your map you can import it.
After importing you have the full map including its textures and can do whatever (in terms of Blender’s abilities) you like (see above). You could even export the model in one of the many different formats and have it 3D printed, something I started to look into – seems to be rather pricey though if you want to go for a size where you can actually see some details 🙂
Do you recognise it? DM4 (“The Bad Place”) without ceilings.