No fossil fuels means other means of a/c are necessary. The Harahappan or Indus Valley civ whatever it was used upwells in big buildings. Imagine you go into a local skyscraper and the bottom floor just has a massive, clean pool. It passively absorbs heat during the day and releases it at night. And it's like that everywhere. Just a reception desk maybe a cafe and a big ass pool on the first floor.