Eglise de Sainte Onenne plays an important role in the social and religious life of this place. It's a nice spot to enjoy a moment of contemplation during a packed travel itinerary.
You'll have sightseeing choices galore when spending time in Trehorenteuc. Eglise de Sainte Onenne is a great place to start here, but there are lots of other worthwhile places to check out. Paimpont Forest, Chateau de Trecesson, and Seat of Merlin are not far from the house of prayer and will fill in your day nicely.