Adding to what Arno said, the region near the Jungfrau has attractive scenery easily reached by public transport.
In good weather, my very favorite easy walk is from Männlichen to Kleine Scheidegg.
Easily reached by cograil from Lauterbrunnen to Wengen, followed by a large cable car from Wengen to Männlichen, the scenery on the way up is spectacular. Once you are up there, you can have a nice lunch at the restaurant and take the easy walk. At Kleine Scheidegg, thecograil train will take you back down, either to Grindelwald or back to Lauterbrunnen.
Although you can do the walk in either direction, it is slightly downhill from Männlichen to Kleine Scheidegg, and I find the views, particularly of the Eiger looming over you as you proceed, to be much superior.
The time table will help you plan the trip:
I've attached some pictures of the region, including some from on or above the beginning of that trail.
One is taken in the very early morning from our room at the Hotel Eiger in Wengen, which is now an apartment building. Other hotels and the plaza near the train station offer similar views.