High density infilling refers to the process of building or developing densely populated areas within existing urban or suburban areas, as opposed to building on open land or greenfield sites. This type of development typically involves the construction of multi-unit residential buildings, such as apartments and townhouses, as well as commercial and retail spaces. High density infilling is often used as a strategy for promoting more sustainable and efficient land use, as it makes better use of existing infrastructure and reduces the need for new roads and other infrastructure in outlying areas. It can also help to revitalize underutilized or distressed urban areas, increase housing affordability and improve walkability and accessibility