Answer:
The septic tank of an abandoned property.
Almost anywhere at a closed refinery (most refineries will never be torn down due to the massive remediation costs involved when they are. Find a good hiding spot there and place the body in the open or bury it)
Numerous quarries are around and most are filled with water. If you ensure that the body will not float to the surface, they are often great disposal locations.
Inside the wall of a home or building - If the body is allowed to desiccate (mummify) then there will be little or no odor. Simply open a wall,insert the body and replaster or drywall it and paint over it.
Underneath an area to be used as a pen or feed lot for domesticated animals. The weight of the animals, plus their manure and the straw placed down to control it will form its own "cap" over the burial site.
In plain sight - The roof of tall abandoned building (hidden from overhead viewing) , an open area in a remote part of the country (after staying there for 2-3 days to see if anyone comes along), or in a storm drain along a lightly used state or county road.