We love Kapla
"A great set, either as your first Kapla or to extend other sets. Once shown a few basic ways to build both my 3.5 year old and 6 year old can create builds independently. The box is great storage and is nice and sturdy - I was worried the plastic cover might break easily, but it's quite thick. The inserts are also removable, so the box can be integrated into builds, or used to store extra Kapla from other sets."