This is a great and creative way to have fun outdoors and learn too. You can set the rules, and the extra equipment that you wish. You can even add mini or action figures to your space. Keeping it small is ideal the examples shown are approximately 2' either round or whatever shape fits the space. For diversity some spaces can be rocky or sandy or have more or less moss and plants. An extension would be to create fairy, elf or gnome houses.
Micro environments can be aquatic too. A small scoop of pond or lake water will reveal an amazing amount of organisms.