Cities4Biodiversity (C4B) participants convened in April 2022 to explore the first of a series of themes critical to the purpose of C4B – developing and supporting a network of cities forging commitments to incorporate climate and nature-based solutions into project design, planning and implementation. Conducted over six days, the Green Cities Deep-Dive Learning included plenary and breakout sessions with presentations from 35 cities in 16 countries. This summary report provides a review of critical insights and expert recommendations from the Deep-Dive Learning, as well as highlights of existing policies and programs from participating cities that promote investment in urban nature.