You might want a container pond.  Take a large Chinese ceramic pot (the ones that are glazed inside and out); if it has a hole in the bottom, plug it with a rubber stopper and seal that in place with aqurium sealer.  Go to your local water garden store and get materials for planting.  They will be able to show you the correct materials, pump and filtration setup.  They will also be able to sell you fish suitable for the size of container you will be using, and a plant or two.  Be sure to lean a rough stick inside so that anything that falls in by accident can crawl back out again.