It’s great if you can do that, but to be frank, a lot of places around the world are not able to provide that. I grew up near the Great Plains of Hungary, which is totally flat and covered in grass, with some patches of black locust trees; totally uninteresting and unsuitable for hiking, and you are either freezing or getting a heatstroke, depending on the season.
But if you travel a few hours you may be able to find something that provides at least an exercise, if not the scenery. I usually organize my holidays with hiking/photography in mind, and use the interim hikes to keep up my stamina and just be outdoors. Depending on where you live, just ask around, and search for “hiking near …”. You may find something nice.
I find Lonely Planet and Rother guides very useful, but also buy local hiking books (even in languages I don’t understand, maps and routes are always useful), and also use websites like outdooractive.com to plan my routes, they give you elevation info etc. Then I download the GPX map to my phone to avoid accidental 5-hour detours just because I missed a turn.