Buy your 3 year old nephew LEGO for these ages or if you are sure its safe buy him a Froebel Toys Kit.
Mother of little Frank Lloyd Wright wanted him as an architect. She hanged architecture drawings to his room and She saw Froebel toys at Chicago World Fair and liitle Frank learned to compose and play with the mass at this age. He used these toys until his death and gave lots of reference to them. His building plans , playing with the window ornaments , stone ornaments everywhere around his buildings , textile designs are all result of Froebel Gifts , they come as number 1,2.. or so and not cheap but excellent.