I think that the English Lake District, where I grew up, must be one of the most beautiful corners of the planet. Covering 880 square miles, it's the largest, most spectacular and, unsurpisingly, the most visited of Britain's eleven National Parks. I think that the last verse of Wordsworth's "Daffodils" could equally apply to the whole Lake District...

For oft, when on my couch I lie
In vacant or in pensive mood,
They flash upon that inward eye
Which is the bliss of solitude;
And then my heart with pleasure fills,
And dances with the daffodils.

The best times to visit, in my opinion, are Spring, when there are lambs in the fields and new life everywhere you look; and Autumn, when the colours, especially when the sun is low in the sky, can be breathtaking.

For self-catering in the Lake District I can recommend Sally's Cottages.