There is also a Parador Hotel on El Hierro. It lies just by the sea, infront of the very famous “Roque de Bonanza”… so you will have a very nice view.
There are lots of things you can do… not just walking 
…. fishing, diving, boat trips, Paragliding.. and so on.
If you want some more information about the Parador Hotel on El Hierro: www.parador.es there are also some nice pictures