This study provides an interdisciplinary account determining how children and adolescents understand urban and architectural aspects of sustainable development. The concept of sustainability implies complex relations between ethical, economical, social, technical and other qualities of our environment. The concept is difficult to understand for children who lack the abilities of abstract reasoning and multi-dimensional thinking. A new measure of sustainability understanding was formed based on pictorial rather than textual format and was applied to a large sample of over 2000 participants aged 6-19years. The results indicated that girls had higher levels of appreciation toward sustainability issues than boys. The results also showed that understanding of sustainability issues increased progressively with age, particularly with adolescents from urban environments. The findings are discussed in terms of cognitive changes in adolescence and their implications for educational policy.