Exterior Hanging Lanterns

I am getting married and I want to hang Chinese lanterns in the place where we get married. The problem is that the columns of the hall is about 50 feet away (this is a large room with a huge vaulted ceiling and columns spaced in the outer wall).

If I use the fishing line does it sag? What could I use? Should I tie it around columns or should I join some other way?

Also, I can not use nails or anything that might damage the building.

Instead of fishing line, you can try a thin wire, which would have less elasticity of the. Try Home Depot or Lowe's to get this in bulk. For suspending the columns, you can use plastic hooks with adhesive on the back. 3M makes a few, and most general stores (eg Target) sell them.

Of course, if there are several lanterns suspended from each wire, you must ensure that the hooks support the weight. Otherwise, they might come from falling during the event! (No bride needs that stress ...) The 3M site shows how the weight of each hook is designed to hold, although I'd go with one that holds more than necessary ....