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Here is a little DIY that is very simple to make, takes about 1 hour and your kids will love it, especially if you have a covered or half covered terrace for those rainy swiss days.
The principle is simple, you need a box which you fill up with sand:)
You can buy all this stuff at your favourite Bauhaus, I have bought 2 x 200cm x 18 cm x 1,8 cm wood boards and 100 kg of sand.
You will also need about 8 wood screws and about 15 nails for the bottom part. I used plywood for the bottom because it's bigger and cheaper than using more normal wood boards for the bottom.
Be carefull if you cut all 4 sides to exactly 1m, you will need to make the bottom 100cm x 100 cm+(2 x thickness of your board) , for me it was 103,6 cm.
Taking this into account, screw in the 4 sides , nail in the bottom and put in the sand, et voila, sandbox ready:)
The only other thing to worry now is if your kid/s will start a sandstorm in the box or not:)