Marais Poitevin

This was a gulf until monks began draining it in the eleventh century, cutting a network of canals that still divides the wet marsh into small plots reachable only by water. The inner zone, the Marais Mouille, is the one people come for: narrow channels under pollarded ash, so overhung in summer that the light turns green, which is where the name Green Venice comes from. Flat-bottomed boats called plates are pushed along with a pole, either self-hired or with a guide who will usually demonstrate the trick of setting marsh gas alight by stirring the bed and holding a flame to the bubbles.

What you actually see

• The green canals - channels roofed by pollarded ash in summer.
• The plates - flat-bottomed boats pushed with a pole.
• The marsh gas trick - guides igniting bubbles stirred from the bed.
• The plot landscape - fields reachable only by water, some still farmed that way.

When to go

May to September, when the ash is in leaf and the tunnel effect works; the canals are bare and open in winter. Boat hire is seasonal and busiest in August.

Honest expectations

Outside the leafy months the green tunnel effect disappears entirely. Self-punting is harder than it looks and shoulders complain. The wider marsh is ordinary farmland; the interest is concentrated in a small area.

Nearby

Niort lies east; La Rochelle is southwest.