Trace around an empty cardboard tube, to cut circles out of thin cardboard (such as an empty cereal box).
Cut four, evenly spaced, slits into the top and bottom of the tube, about as long as the radius of the cardboard circles...
...so the circles will slip nicely into the slits.
Add more circles and tubes.
Then, you can build...
...build to your heart's content, or until you run out of tubes and circles.
And when they all fall down, they're much quieter than blocks too. Making them a good choice for building when Daddy is napping.
Sorry about the gloomy pictures, but we're finally getting some real snow - making for a lovely, if dark, winter's day.
It's great to be a homeschooler.