Two very different day trips sit within easy reach of Shanghai, and which one suits depends entirely on how the legs feel the morning after 42.195 km.
Suzhou is the more ambitious of the two. High-speed trains leave Shanghai Hongqiao Railway Station roughly every 10 to 20 minutes and reach Suzhou in about 30 minutes, making it one of the easiest big day trips from any major Chinese city. Zhujiajiao, a water town on Shanghai's own western edge, is closer in spirit to a village than a city and involves a coach or a Metro-and-bus combination of around an hour each way. Neither requires advance planning beyond buying a train ticket or checking a coach timetable.
The choice is really about pacing. Zhujiajiao is flatter, smaller and easier to cover slowly. Suzhou rewards the trip with real depth, classical gardens, canals, a proper old town, but asks for more walking to make it worthwhile.
Suzhou's classical gardens
Suzhou's UNESCO-listed gardens, most notably the Humble Administrator's Garden and the Lingering Garden, are compact enough to visit one or two in a single day without exhausting recovering legs. Paths are paved and mostly flat, with benches and covered walkways throughout. Picking one garden and taking it slowly beats trying to see all of Suzhou's famous sites in a single day trip.
Suzhou's old town canals
The Pingjiang Road canal-side street runs through the old town with water on one side and traditional shopfronts on the other, entirely flat and well suited to an unhurried walk with frequent stops for tea or a rest.
Zhujiajiao water town
Zhujiajiao, much closer to Shanghai, offers a quieter, smaller-scale version of the same canal-town character: stone bridges, waterside lanes and a manageable size that can be covered in a couple of hours without much walking. It is the better choice for legs that want the canal-town character without the distance.
Getting back
Suzhou's high-speed trains run back to Shanghai Hongqiao until late evening; buy the return ticket on arrival to avoid a wait later in the day. Zhujiajiao coaches and buses run less frequently, so check the return schedule before setting out.