There was a full-color illustrated book at least 20 years ago. Each page was edge-to-edge covered with a cross-sectional view of cities, usually underground or inside plants, of dozens of tiny people (possibly mice?), going about their daily business. They often had sort of improvised technology, or had built devices into natural facades, like a periscope that looked like a flower. The illustration style was very realistic and extremely detailed.
I wonder if you might be looking for Trouble for Trumpets by Peter Cross and Peter Dallas-Smith? http://petercrossart.com/books/trumpets/trouble-for-trumpets/
My goodness chanda, that is exactly what I was thinking of! It’s not quite how I remember, but they are wonderful. I’m so glad you knew what I was talking about!
This sounds like the illustration style in the children’s books put out by the Medici Society, London. You could try looking at some of the books by the authors in their series of picture story books: Molly Brett, Racey Helps, Jean Gilder, Truda Mordue, Sandy Nightingale, Fiona Owen, Audrey Tarrant or Margaret Tempest.
this made me think of the brambly hedge books, I realise this is now solved, but just in case anyone else is hunting for similar