Check out Flying Castle island 3D model on CGTrader for $24.99. High-quality Polygon mesh mesh by Hafcoy.
STL (Stereolithography, filesize: 154 MB), OBJ (OBJ, filesize: 154 MB), 3DS (3D Studio, filesize: 77.1 MB), BIP (KeyShot, filesize: 154 MB), FBX (Autodesk FBX, filesize: 154 MB), SKP (Sketchup, filesize: 77.1 MB), GLTF (glTF, filesize: 77.1 MB)