Being a small island, a walking holiday in Formentera would be ideal. The only problem being that the island is long and narrow and the towns and villages are spread out, so arranging daily accommodation could be a problem.  A better proposition would be a cycling holiday, the island is mostly flat making it ideal for bicycles.  Being only 19 kms long, getting from village to village is not a problem.  There are hotels available in the larger villages, or bed and breakfast accommodation in most places.