The grass is ugly, the trees are okay and the houses are =|. Also, it's in 2.75D. Makes it horrible.
Ugph. Uhm, well, the placement of the rocky-things is really nice. Random but not overly done. The shape of the cave is nice as well, and the large cavern spaces make it really realistic yet to the game as well. The fact that you can go back to the cave later and find something else (it's not compulsory, right?) is cool too. I'm supposing that little block to the left contains some sort of item, which is, once again, awesome and incredibly in-character with the game (can't think of any other word, lol). The shape of the map is really nice, and although it might get tight in some places, it's generally really playable.
However, the mountain gap parts just south of the top path, south of the surf-exit and to the right of the south exit irk me. If you just joined them together, I'd think they'd look smoother.
Is that in-depth enough for you? xD
Also, I have a map.
Zubat Cavern:
Self-explanatory, right? xD