. . . the places specially devoted to children's play - ADVENTURE PLAYGROUND (73), CHILDREN'S HOME (86), CHILDREN'S REALM (137) - and THICK WALLS (197)-can be embellished with a special detail.
Children love to be in tiny, cave-like places.
Therefore:
Wherever children play, around the house, in the neighborhood, in schools, make small "caves" for them. Tuck these caves away in natural left over spaces, under stairs, under kitchen counters. Keep the ceiling heights low - 2 feet 6 inches to 4 feet - and the entrance tiny.
In the course of their play, young children seek out cave-like spaces to get into and under-old crates, under tables, in tents, etc. (For evidence see L. E. White, "The Outdoor Play of Children Living in Flats," Living in Towns, Leo Kuper, ed., London, 1953, pp. 235-64.)
When children are playing in such a "cave" - each child takes up about 5 square feet; furthermore, children like to do this in groups, so the caves should be large enough to accommodate this: these sorts of groups range in size from three to five - so is to 25 square feet, plus about 15 square feet for games and circulation, gives a rough maximum size for caves.