On Friday, October 29, 2021, an International Lecture Series 2021 activity was held with the theme The Future of Sea Cities. The theme of this sixth series of activities is related to the 11th Sustainable Development Goal on Sustainable Cities and Communities, and the 14th Sustainable Development Goal on Ocean Ecosystems. The number of participants in the 2021 International Lecture Series this time is 95 participants who come from the academic community and alumni of Diponegoro University. On this occasion, also present Prof. Dr.-Ing. Joerg Baumeister as the originator of the Sea Cities concept from the Sea Cities Lab, Cities Research Institute, Griffith University, Australia. In his presentation, Prof. Dr.-Ing. Joerg Baumeister explains the concept of Sea Cities and some examples of Sea Cities projects in Australia. The next session was followed by a presentation from Mr. Rukuh Setiadi, Ph.D from the Department of Urban and Regional Planning about his research entitled “The Future of Jakarta in Sea Cities Perspective”. In this activity, Mrs. Wido Prananing Tyas, Ph.D. acted as the moderator of the activity who guided the exposure session, discussion until the end of the activity. From the two explanations, it can be concluded that Sea Cities is a comprehensive coastal urban development concept, including lifestyle and activities on the water in order to respond to the issue of climate change and sea level rise. Sea Cities combines mitigation strategies as well as adaptation to environmental and climate change issues related to sea level rise.