A simple vase based on a twisted plus sign. Or an "X," if you prefer to look at it that way. It can be two things.
This .stl is a solid object that y...ou need to convert to a vase at the slicing stage. In Slic3r, you do this by telling it to have zero infill and zero top layers. Then the wall thickness is determined by the number of perimeters - I used two and it worked well.