The Ihlara valley is very nice. Removed a little from the rest of the Cappadocian sites. it can be a little tricky to get to but it's worth a full day if you can spare one. The gorge is 16 km long and both sides are lined with rock carved churches, about 100 in all. You can look at the more important of these in a couple of hours but it's very pleasant to spend an afternoon following the river down the valley and exploring on your own.
The climb down to and especially up from the gorge can be demanding and probably shouldn't be attempted if you're feeling frail. To make the most of your time here a full day and a picnic is a good idea and will repay the effort in terms of a relaxed days pottering about admiring the churches and the valley's beautiful scenery.