Waterfalls
Fountains can be created out of most anything as long as you don't plan to have fish or plants in your pond. If you do plan to have fish or plants, you need to research and consider the materials you plan to use.
Also, some metals such as copper which turns green when exposed to water can effect the elements that your pond is made of. On one hand though, this may be desirable for some garden design ideas where you want to create an aged or colored look in the landscaping or garden.
