The original spec for WKT (Well Known Text) geometries did not include (to my knowledge) support for 2D curveys, like circular arcs. I didn't realize that had changed, and the WKT spec now includes some limited support for 2D curves. You can see this paper for more information:
This is cool, because I will need support for circular arcs in WKT if I am ever get around to working on a linear referencing (route stationing) application for flood control levees. I don't think will be seeing support for these curves in JTS anytime soon (because of the complexities that it introduces), but I wonder if we might find room for it in Geotools?
The Sunburned Surveyor