There is a branch of the Denver Botanic Gardens in the Highlands Ranch area. The gardens are so beautiful, we definitely recommend you check them out!
Beautiful park with walking trails, a lake with kayaking, and beautiful scenery.
This is just one of the many amazing breweries in the Denver area. We highly recommend you check out a brewery while you are here! The Coors factory is over in Golden in you are willing to drive.
Downtown Denver is a little further away but it's worth the trip. You can also take the RTD if you do not want to drive. There is tons to do in Downtown but Larmier square is a good starting point!
Go check out the big blue bear outside the convention center and then spend some time downtown! There are plenty of bars, shops, and restaurants in the area. You could walk to Coors Field, where the Rockies play, or hit up one of the several market/food halls in the area!
A must see if this is your first time in Denver. We recommend going during the day or at sunset, provided there is no event there that night.
If you want a little more nature, this is a great place to check out. It's about 30 minutes from the Highlands area. Cherry Creek State Park is also beautiful! There may be an entrance fee for the state parks.