Park in the free car park on the D33, 1.4 km from the château in the direction of Crouy-sur-Cosson. This car park is not signposted from the road; it is accessed via a driveway.
(S/E) Follow the Cosson towards the château on its left bank (do not change banks from the car park). Walk along the south-east side of the château, then go around it (château on your right), climb the stairs leading to the bridge over the Cosson.
(1) Once you have crossed the Cosson, move away from the castle by taking the curved path. At the Rond Prince Louis, head in the opposite direction to the castle by taking one of the two parallel paths. At Rond François 1er, take theGR® Blanc et Rouge marked path on the right, turn left and cross the François Ier road, then take the path opposite.
(2) Leave the lane when it turns left, go through the gate and continue to the right along the Sentier des Parquets Assegonds. This path curves sharply to the left and climbs slightly, crossing the Route Princesse Élisabeth, then meeting the Route de la Reine with a view of the Pavillon de Saint Dyé on the left.
GR®3White-Red markings
(3) Turn left onto the lane called Route de la Reine. At the Pavillon Saint-Dyé, head towards the Rond Prince Sixte on the right.
(4) Leave the Chambord park and take the lane on the left that follows the boundary wall outside the park (wall on your left).
(5) Do not continue along the grassy path alongside the wall, but follow the dirt track as it turns right at the edge of a small wood, which it bypasses on the left to reach an intersection. Take the path on the right, ignoring the turn-off on the right.
(6) At the crossroads, turn left, leaving the lane for the grassy path, ignoring the turn-off on the right. This grassy path becomes a dirt lane as it approaches the houses and is called Chemin de la Roture.
(7) At the intersection, take Rue de la Tuilerie on the left, which you will quickly leave in favour of the first path on the right, Chemin de la Plaine, which is initially paved and then becomes a dirt track at the exit of the hamlet of Bouesse.
(8) Stay on the grassy path just after the pond, crossing the Pointe des Cotes Noires.
(9) Turn left at the tarmac lane. At the crossroads, keep left, ignoring the two lanes on the right.
(10) Shortly after the next crossroads, ignore Rue de Saumery and turn left onto the grassy path. You will see Château de Saumery on your right, before a T-junction.
(11) Turn right to reach the Pavillon de la Chaussée. The path becomes paved and then leads to Rue de Saumery, which you will take to the left. Cross the Cosson, which you will see on your right.
Signposted "La Loire à Vélo"
(12) At the crossroads, turn left and enter the Chambord park, heading towards Chambord. Quickly leave the road by turning left, go through the barrier, and follow theGR®3(La Loire à Vélo route) to a four-way crossroads.
(13) (Water lovers can admire the Cosson river, located about 200 metres away, by taking a detour along the path on the left.)
Follow theGR®3to the edge of the castle. At the end of the path, go through another barrier, then turn right at the T-junction.
(14) Turn left at the four-way intersection (Rond Charles X) onto Route Charles X D33 (caution), in line with the castle. Pass Route François Ier (D112) and the car park on your left. Opposite the castle, turn onto one of the paths on the left to cross the Cosson as you did on the way there.
(1) Once you have crossed the Cosson, take the lane on the right to follow the winding river on your right, then cross the Pont Saint-Michel to return to the starting point (S/E).

great. Thank you both