Complex sentence: The small village of Glencastle has some very interesting very large mounds in the narrow valley that are not naturally occurring, seen on the right hand side, close to the roadside on the approach to Belmullet from the east.
Split into simpler sentences: The small village of Glencastle has some very interesting very large mounds in the narrow valley that are not naturally occurring. They can be seen on the right hand side, close to the roadside on the approach to Belmullet from the east.