Linton Falls is the simplest good walk from Grassington: down from the village to the River Wharfe, across the bridge, and along the water to a low, rocky fall below Linton. It is close enough for a quick stroll but still gives you the river, fields, and limestone edge that make Wharfedale so satisfying.
The falls are best after rain, though the paths can be muddy. Combine them with a loop through Linton village if you want a gentle half-day rather than a hill walk.