The route leaves Nantes along the Erdre, a river canalised as early as the 18th century, well before the rest of the canal was dug, before joining the Isac near Blain, where a medieval castle that once guarded the crossing still stands.
The towpath, well maintained and clearly marked on this section, runs past a string of manually operated locks typical of the early 19th century — some still worked by hand by lock-keepers for the rare pleasure boats that still use the canal.
Guenrouet, a small riverside town midway through, makes for a pleasant rest stop before reaching Redon, a town straddling the border between Loire-Atlantique and Morbihan, where the Isac flows into the Vilaine.
Indicative distance for this stretch.