In reply to alasdair19:
Harrop Tarn is my go-to easier walk. Start from Dob Gill car park west of Thirlmere to go up to the tarn, and then keep going past the tarn and down the forestry track and back along either the road or lake path. You can swim in the tarn with a view of Helvellyn, and there are some good views on the descent too.
A really gentle option is Heughscar hill from Helton common to reduce the ascent (otherwise start from Askham, Pooley Bridge or Roe Head, especially if it has been wet or you might get stuck in the mud when parking). Good views down Ullswater and Askham has an outdoor pool.
Low Fell from the big layby north of Loweswater lake has better views than either, but might be too far and too west.
I would also second High Rigg, Aira Force (& Gowbarrow), Bowscale, and Dodd that others have already posted.