Potteric Carr is Doncaster's best nature escape, a Yorkshire Wildlife Trust reserve of reedbeds, pools, wet woodland, and paths just south of town. The reserve is especially good for birdwatching, with hides overlooking marsh and open water, but it is also a useful place simply to walk when the town centre has worn thin.
Allow more time than the map suggests. The paths loop through different habitats, and the experience changes with the season: warblers and breeding birds in warmer months, wintering wildfowl and sharper light in the cold. The visitor centre makes it easy to treat as a half-day rather than a quick detour.