A green belt is a land classification policy used in urban planning to conserve areas of wild vegetation or agricultural land around urban centers, protect the environment and densify. When it comes to linear structures that can cross the city instead of surrounding it, they are called greenways "Greenway (landscape)").

Among the objectives of the green belts are:.

• - Protect the natural environment by avoiding urban sprawl.

• - Improve air quality in urban areas.

• - Densify the population inside the belt, thereby reducing the per capita impact.

• - Ensure that inhabitants of large urban centers have easy access to natural areas, without having to travel long distances.

• - Protect the rural character of towns located near large cities that, if the green belt did not exist, could be annexed to the city due to the expansion of its suburbs.

In this regard, the doctor of law and urban planner Joan Amenós Álamo comments that "The English formula of green belts has been one of the most applauded as a radical urban barrier. Although its mechanical nature and its inflationary effect on other properties have been criticized, a large sector is in favor of its maintenance and untouchability."[1] Although the original objective of the London green belt has been met, not all the consequences are positive, since it seems to generate gentrification. by not capping the price per square meter.

The ability of green belts to achieve their objectives may differ depending on the country and city in which they are implemented. The attempt to keep small population centers separate from the large city so that they function independently is sometimes not achieved and peripheral population centers, even when separated from the city, function as satellite cities rather than as independent cities.

However, it has been shown that "limiting the increase in urban areas in a given territory, reducing damage to the environment", through the historical comparison of 60 European cities between 2006-2015,[2] half of which implemented urban green belts. 90% of cities that have a green belt have experienced a decrease in urban expansion during the period considered, compared to 36.7% of cities without a belt that have also reduced their expansion. Among the conclusions of this study are that.