Before I read the altitude limitation, I thought of Berner Oberland in Switzerland. You are able to combine various moderate hikes with train and gondola rides.

I would really consider the BO in Switzerland. We stayed in Lauterbrunnen for 8 days and hiked everyday. It was great. There are tons of beautiful hikes throughout the region, from easy to difficult.

Do you have an issue with the altitude or just being cautious? Just because you are at a higher elevation does not mean you cannot hike. You just pace yourself differently and listen to your body. Pick the less strenuous hikes if you need to.

Would Interleukin make a good base or any other suggestions. Lauterbrunnen noted.

I would imagine Interlaken would be a good base also. I am not familiar with hikes other than the BO area. It will take you anywhere from 20-45 minutes to reach the hikes in the BO area via train.

I loved doing what you described for a week on the Isle of Skye in Scotland. But I had a car to take me to trailheads.

If you are not talking about the peak of summer, hiking in the Sorrentine peninsula and along the Amalfi coast is famously beautiful. Ligurian hills of the Italian Riviera (not le Cinque Terre, but closer to France) is popular with Belgians and other northern Europeans (look around Triora). Sardegna might be right for you, but it is pretty rough trekking.

If you want high summer, I think you can avoid the altitude issues but still be cool in the valle d'Aosta in places around the Gran Paridisso Park (Cogne, Lillaz, the Val di Rhemes, Valsigrenche) , but you would want to move locations more than once I think. You can reach this area very easily by train from Milan.

You can probably find somewhere to stay on any of the following lakes in italy -- Lago di Como, Lago di Garda or Lago Maggiore -- and use boats to get around the lakes and take different hikes every day. I think you could even do that in high summer.

I would also check into the Picos in northern Spain. I have read spectacular things about walks there at all levels. You can also probably go from town to town at lower levels of the Pyrenees of the French side and have lovely, lovely walks in early summer or early fall.

My impression is that most people stay in Interlaken because the can reach the highest peaks easily from there. I would opt for other areas of Switzerland while you will pay less, find fewer tourists, and still enjoy lovely scenery if you are not interested in going up to glaciers.

The BO is lovely - but it does depend on your capacity to walk at altitudes. Some of hte towns are at 5 ot 6K feet and walks go up from there. Unless you are used to it - it can be really exhausting.

And for someone with any sort of lung problem can be dangerous.

Perhaps you already know what altitude you can easily handle - or can consult with your MD.