sidewalks on slopes

[Guime]

im not really new to revit but i dont know where else to post questions like these.

im modeling a shopping centre and its context.
the site is sloped at various angles, thus, the toposurface is aswell.
i want to model the sidewalks, as it will be about 200mm high on top of the toposurface, my idea was to create sweeps, with the toposurface as a workplane. seems you cannot select the toposurface as a workplane.

how would you go about modeling the sidewalks on a site with various slopes?

(a subregion would have worked perfectly if it could have a height)

[Elmo]

You could most likely achieve it with either Ramps or custom floors. I like the idea of custom floors because you can edit the ends individually to different heights.

[patricks]

You can do floors and edit the various points to correspond to the elevation difference below the host level of the floor. It can get rather tedious, though. Also you'll need to turn off the Internal Edges subcategory under Floors in any view where the sidewalk floor shows up so that you don't see all the warp surface edges Revit will put in there.