Body Farms:

In 1981 a forensic anthropologist named Dr. William M Bass started the first “Body farm”; a facility to study human decomposition, behind the university of Tennessee medical center. 

The facility consists of a razor wired perimeter, which contains a two acre wooded area with bodies placed in different areas. The decomposition of the cadavers are recorded in great detail. These records aid investigations and help to further understand what happens to the body during different stages of death. The bodies are either donated via individuals who register before death, or donated by the families of individuals. This provides the facility with around 100 bodies per year, with 1300 people currently registered as donors.

Sources: https://en.wikipedia.org/wiki/Body_farm
http://www.express.co.uk/life-style/science-technology/431287/We-need-human-body-farms-says-real-life-Dr-Bones-and-forensic-expert-Anna-Williams
http://video.nationalgeographic.com/video/body-farm-sci