My friend(TurbTastic) and I have been making Mario Kart 64 remakes. This is my version of Bowser's Castle. I used an overhead view as well as had the game itself playing to capture as many of the aspects from the N64 version as possible. There are numerous versions of Bowser's Castle already out there but I feel that this map races better compared to the rest. Instead of using falling blocks that only reset every 30 seconds or so I used falling fusion coils that fall through flipped over teleporter frames (see attached pics). It makes for an exciting 8 person race. Hope you enjoy it! If you like this check out our other maps! I also have Sherbet Land, Banshee Boardwalk, Yoshi Valley, and DK's Jungle Parkway on my fileshare (Kalimari Desert coming shortly). My buddy (TurbTastic) has Koopa Troopa Beach, Toad's Turnpike, Frappe Snowland, Choco Mountain, and Rainbow Road (which has over 24,000 downloads already!).
Looks alright, my biggest concern is how "small" it feels. A lot of spaces feel very tight where they didn't feel that way in Mario Kart 64. I would recommend widening the track in a number of places and turns.
There's an n64 Bower's Castle on the top downloaded/recommended somewhere. They did a really good job, despite lacking a slight shortcut. You should check it out for some inspiration. I recommend using the circular incline ramp small for the tower you go around before the final stretch.
Finally a map that lets me relive the maddening frustration that made me want to snap someone's neck in the original Bowser's Castle 64 Mario Kart map. </sarcasm>