The area of northeast Iceland is great for both long and short trips. I like to travel in areas that are not the most stressed tourist attractions. It is usually possible to be completely uninterrupted by others by walking in other areas than all the others.
Here you can find pictures and descriptions of tours starting at Geyteyarstrønd 4.
The tours vary from walking or cycling which takes a few hours to day trips by car.
These are usually not described by tour operators.