I found a possible solution:
[Route("things-to-do/{filter1}/{filter2}/{filter3}/{filter4}/{Area?}", Order = 1)]
[Route("things-to-do/{filter1}/{filter2}/{filter3}/{Area?}", Order = 2)]
[Route("things-to-do/{filter1}/{filter2}/{Area?}", Order = 3)]
[Route("things-to-do/{filter1}/{Area?}", Order = 4)]
[Route("things-to-do/{Area?}", Order = 5)]