I would be tempted to stick a stick in it to see how deep it is. The stick might tell you if it has something in it like electrical.
We have several pipes in the ground that look similar to that. Some are associated to our septic system, some are associated as a cleanout for plumbing, and one is connected to the septic to dump our RV. I wouldn't expect any of them to smell.
It might be filled with either rainwater or your water table. I would do research before trying to pump it out.
Are you buying the property or renting it? A call to the former owner would tell you what it is.
If it is related to a septic system there would be records on file with the county. Do you have a Annual Maintenance Service Contract? If so, your service contractor might know what it is. Aerobic and Drip systems require a maintenance contract.
Since you show "DFW" I assume you are in Texas. There are strict laws regarding property less than 10 acres.
Basics for Septic Systems
Permitting a Home System