I have been asked (and said yes before thinking) to make a b-day cakefor two little boys for the Sat. after Thanksgiving. I have plans for Thursday, Friday, and Saturday so I need to have it done by Wednesday. So it needs to be able to hold up for a few days in a fridge. That being said. Any ideas? All I know about the mud track is that its kind of horse shoe shaped....The lady is supposed to be giving me some Hotwheels sized trucks to put on it, other than that I'm on my own!
I did a cake a year ago for my nephew's birthday that was a full sheet cake. I formed mountains and hills out of rice krispies treats, then iced the top of the cake in brown and the sides in green. I made the track using oreo cookie crumbs (just the cookie - not the white filling included). I made boulders by marbeling brown, gray, tan, and black fondant together by hand. I piped grass as a border and around the boulders. I then placed toy monster trucks on the track. My nephew really liked it. I had to make it well in advance and transport it 200+ miles to my sister's house - it held up beautifully. I'm sorry I can't find pictures of it to post for you, but perhaps you might be able to use some of the same ideas. Hope this helps!
Recently, Ace of Cakes did an episode with a cake that featured an "off road" type track. One of the cute things they used for the true looking track was an actual toy (motorcycle in this case) run around the track to imprint its marks. Duff reminded his viewers to think out of the box when it comes to being creative with how to achieve certain effects. Ahartman has a lot of good ideas in her post. As well, I made a monster truck for my nephew and Hershey's chocolate syrup for the mud. It holds up well and stays in place. Good luck with your cake and, have fun!