West of Rambouillet forest the land loosens up into a patchwork of wheat, copses and small river valleys, and this stop sits in that gentle seam between the Yvelines and the Eure-et-Loir. Épernon is the nearest proper town, a few kilometres off, built where the Guesle and the Drouette meet before they wander on towards the Eure. It is quiet country, and after a day on the Seine loops it feels like the ride is exhaling.
The name may ring a bell. The dukes of Épernon took their title from this little town, the best known being Jean-Louis de Nogaret, the swaggering favourite of Henri III who outlived several kings and most of his enemies. A short hop south-west brings you to Maintenon, where the arches of Louis XIV's unfinished aqueduct still stride across the château grounds, a monument to a plan to send the Eure to the fountains of Versailles that war and money eventually killed.
As for water you can actually get into: the rivers here are narrow, shaded and better for looking at than swimming in. The realistic option is the string of étangs de Hollande inside Rambouillet forest, to the east, which has long had a summer bathing area. Check that it is open and supervised before you plan around it, because rules on these ponds change with the season and the water quality.
The riding is easy rather than dramatic. Narrow departmental roads run between fields and through villages with grey stone churches, with the occasional slow tractor and a lot of deer warning signs, which mean it around dusk. Surfaces are generally decent but patched, and gravel collects at farm entrances. Wind can push you around on the open plateau when the forest edge falls away.
Épernon has the shops, cafés and fuel you need, and Rambouillet, with its château and the royal dairy built for Marie-Antoinette, is close enough for a longer break if the day allows. Otherwise take the cool of the trees, a drink, and the slow road home.