I hope this is not off-topic, but you can deepen the observations of life in almost any square meter by making a Winogradsky column from a soil or mud sample. Microbes will proliferate at different depths and they will show up as bands of color. This may not lend itself to iNaturalist posts, but it is an awesome project (I just led a workshop on this over the weekend). It highlights how full of life soil is and demonstrates how microbial communities interact.
https://serc.carleton.edu/microbelife/topics/special_collections/winogradsky.html