How do you get to the upper level in Tomb Town?

Go to the second race track, then slightly to the right. Walk up to the park worker, then jump across the water to the left (the one without the gates). Follow that path until you get to the button. Dive on it, and then head back to the worker. as you approach the worker from the button, you should see a statue of a face. just in front of that is a platform that will go up to the upper level. (The statue in question is just on the right as you first enter the "inside" section)