These are the kind of tubes used to mail large photographic prints or posters. About three inches in diameter and three feet long. The walls are about a quarter inch thick.
I have about two dozen of them.
So, gimme some ideas on fun activities to be had with giant cardboard tubes. Bonus points if it’s a fun activity that could be had with a paper-towel or toilet-paper tube, but which would be markedly improved with the use of a giant tube.
Make a musical instrument - assemble them into a long rack (parcel tape will probably do the job), and cut them to different lengths. Play by whacking the tops with a table-tennis racquet (or anything similar).
I am stunned that you even needed to ask. Fencing, of course. Christmas wrapping paper tubes never lasted very long (and there was always the risk of incurring Santa’s wrath if we got too violent) but your tubes should make for hours of fun. En garde!
You could cobble together a really neat indoor junglegym/multi-tree-perch thingie for someone’s pet cat or parrot, even. You could wrap the tubes in various animal-pleasing shredding materials like sisal/jute twine/rope, burlap, carpet, etc. Would make for an exceptional gift for a cat-lover friend, or an interesting (and potentially lucrative!) offering on Ebay.