Complex sentence: The tribe is situated at Kitselas, British Columbia, at the upper end of Kitselas Canyon on the Skeena River, once a great trading nexus, just outside of and upriver from the city of Terrace.
Split into simpler sentences: The tribe is situated at Kitselas, British Columbia, at the upper end of Kitselas Canyon. On the Skeena River, it was once a great trading nexus, just outside of and upriver from the city of Terrace.