Play makes dogs happy and is great exercise but it also helps control weight and support good mental health. (cincinnatilabrescue.org)
Aside from the physical benefits, walking can also make your dog happy. (bigskydogs.com)
You can even plant grass on the top to really make your dog happy (for some reason, many dogs prefer to attack lush green grass rather than raw dirt). (dogobedienceadvice.com)