Look up "Barcelona grid plan" and see the pictures! This city plan was designed to let in light and allow for easier movement of air and people. The edges of each unit were designed to be rounded to allow for smoother vehicle turns, and green spaces are also incorporated to improve quality of life.
Barcelona is facing rising temperatures, similar to other regions in Spain. The climate is also getting drier, and summers have become longer in the past half-century. Air pollution and waste control are concerns with Barcelona's population density and intense tourism. Sea levels are also rising, which can threaten coastal areas. While I was here, coastal Spain experienced some severe rains. The Barcelona airport was flooded and Valencia, a region south of Barcelona, was severely flooded, leading to many deaths.
Barcelona has waste management and street cleaning systems to keep the city clean. There are large waste bins for different waste categories all around the city, and I regularly see street cleaners washing the streets with hoses or with small trucks with hoses. Greenery is also present throughout the city, which boasts many trees and parks. There are some notable sustainable buildings, such as the Torre Gloriès, an artistic building that gets all its energy from its built-in solar panel technology. To create more living space, a top floor was added to some buildings in Barcelona in the 20th century, too. In response to the environmental stress posed by tourism, Barcelona has been enacting policies and tourism management to promote more sustainable levels of tourism.