Check out Modular Bunker WWII Low-poly 3D model on CGTrader for $49. High-quality mesh by KangaroOz3D: 7732 polys, 9424 vertices. PBR, Textured, UV Mapped.
BLEND (Blender, filesize: 13.4 MB), OBJ (OBJ, filesize: 268 KB), FBX (Autodesk FBX, filesize: 2.01 MB), GLTF (glTF, filesize: 852 KB), DAE (Collada, filesize: 699 KB), TEXTURES (Textures, filesize: 1.87 GB)