Lagos, also known as Lagos City, is a large city and port in southwestern Nigeria. As of November 2025, the city’s population is estimated to be between 17 and 21 million people. This makes Lagos the largest city in Nigeria, the most populous urban area in Africa, and one of the fastest-growing megacities in the world.
Karura Forest is an urban forest in Nairobi, the capital of Kenya. It is the second largest urban forest in the world, following the Tijuca Forest in Rio de Janeiro, Brazil. The forest was designated in 1932 and is managed by the Kenya Forest Service along with the Friends of Karura Forest Community Forest Association.
Medellín, officially known as the Special District of Science, Technology, and Innovation of Medellín, is the second-largest city in Colombia after Bogotá. It is the capital of the department of Antioquia and is located in the Aburrá Valley, a central area of the Andes Mountains in northwestern South America. According to the 2018 census, Medellín’s population was 2,427,129.
Freiburg im Breisgau has parks, green areas, playgrounds, and other spaces for recreation, totaling 397 hectares (980 acres). This equals 18.05 square meters (194.3 square feet) of green space for each person living in Freiburg. On average, major cities in Baden-Württemberg provide 22.66 square meters (243.9 square feet) of green space per person.
The Carbon Neutral Cities Alliance (CNCA or “Alliance”) is a group of major cities worldwide working together to reduce greenhouse gas emissions by 80% or more by 2050 or earlier. This goal, called “80×50,” is the most ambitious plan for cutting emissions among cities globally. The Alliance studies how leading international cities can achieve these large reductions in emissions and how they can cooperate to reach their goals more quickly and successfully.
The Netherlands has a strong and well-developed economy focused on trade, logistics, manufacturing, services, innovation, technology, and renewable energy. It is the 18th largest economy in the world by nominal GDP and the 28th largest by purchasing power parity (PPP). It is the fifth largest economy in the European Union by nominal GDP.
Urban agriculture is the practice of growing, preparing, and delivering food in cities. It also includes raising animals, growing fish, keeping bees, and planting gardens in urban areas. This is different from peri-urban agriculture, which happens in rural areas near cities.
The Singapore Green Plan 2030 is a plan created by the Government of Singapore on February 10, 2021. It sets goals for making Singapore more sustainable by the year 2030. This effort involves all parts of the nation and helps Singapore work toward achieving net zero emissions by 2050.
Cool pavement, as defined by the United States Environmental Protection Agency, is pavement that uses special technologies to help reduce the heat island effect. Most cool pavements either increase the surface’s ability to reflect sunlight, which helps keep heat from reaching the ground, or use water to cool the air around them. Newer methods include collecting energy, storing heat, and using materials that change state to manage temperature.
The urban heat island (UHI) effect is a weather and climate-related phenomenon where cities are much warmer than nearby rural areas. The temperature difference is often bigger at night than during the day and is most noticeable when there is little wind, during calm weather, and in summer and winter. The main reason for the UHI effect is changes to land surfaces, while heat from energy use is a smaller cause.