Marietta Square is a such a fun place to hang out for the day. Our favorite coffee shop there is Cool Beans. They have delicious house roasted coffee as well as a neat eclectic vibe inside. Their are also delicious restaurants available like the famous Marietta Pizza Company, The Local (Thomas and I's favorite), WR Social House and the new food hall that is now on the square. After you eat there are many antique shops, art galleries and other shops to walk through.
If you're looking to get a little exercise in, then we suggest Kennesaw Mountain. It is only 15 minutes from the Marietta Conference Center and about a one mile up and back hike with lots of scenic views.