There is no such a thing as an invisible track :) its most likely an IBEAM track. Which is a thin white metal that can be bent into shape and if you ceilings is white its not very noticeable when its open

thank you. if I'm planning on using the IBEAM , not from one wall to another, but actully for a lenght of 80'' , can I put some stopper at the end/edge of this - due to the fact that there is no wall to act as a stopper?

The track is embedded in the ceiling, so when the curtains are open there is a small gap you can see.

These are terrifically elegant drapes . Where could I purchase these?

Can you tell me more about the tracks and embedding them in the ceiling?