We saw this beautiful little pond on the porch of some friends in Switzerland. As you can see, it is made of a plastic storage box, and contains rocks and aquatic plants. There were some frog eggs attached to one of the aquatic plants the family bought, and the lucky children who live here have been watching the tadpoles develop.
Here is a closer look. If you decide to make one, supervise the children when they are around your little pond. This pond is on a table top. It is low enough so that the children can see into the pond, but high enough that they won't fall in.