I really love Tilden Botanic Garden. For one thing there are about one million little bridges. And there is just a pleasing variety of microclimates and fab plants.
On our last outing there we sat around and used nature to make some tiny, ephemeral art. The second one is a nudibranch or maybe a paramecium. I realize a botanic garden probably isn't the right venue for this but I did it anyway and it was pleasing.