The secret tape is hidden in the banks and there are two ways to get there: you can access the subway and ride along the track or wallride the brick wall and hop over. Either way requires you to get the five subway tokens first. Once you're there, ride along the grey path until you reach the end, where three rebars are sticking out of the path. Grind the longest rebar and then ollie to the left to land on another rebar. Grind it to the end for the secret tape.