Boston is often referred to as a city of neighborhoods because of the abundance of diversely populated neighborhood districts within the city. This is largely due to most of Boston’s current land area not existing when the city was founded. Instead, it was gradually and naturally created without forming a grid and was built around forestry and other natural obstacles. While this lack of centralized planning did cause housing issues in the 19th century and promoted the growth of slums and sprawl, the city planners of Boston have made great efforts to combat this and ultimately turned these challenges into opportunities to restructure and improve the city.