An amazing Park to do some hiking and take in the mountains.
If you would like to take in some nature but with less of a drive/climbing then Denver Botanic is perfect for a relaxing stroll and lovely afternoon. Also, it back's up to the ceremony site.
For those who didn't take the train in, Union Station is a great starting point for a day. Snooze AM Eatery is one of the best breakfasts you'll ever have and you are surrounded by the LoDo area which is great for walking around and taking in the city.