Castillo de Petrer
Built late twelfth century or early thirteenth, but like many others, was built on an earlier watchtower. It had a function of territorial control: controlled the passage of the Castilian plateau to the Mediterranean, and the other way around.
Castillo de Mola
A rare Almohad building (also built on Roman remains) of the twelfth century. A windowless tower and is one of the oldest buildings in civilian use in the Valencian Community.
Palacio de Altamira
This palace in the heart of the city of Elche, located near the riverbank of Vinalopo’s river, was built in the late fifteenth century by the noble Castilian Gutierre de Cardenas (First Lord of the city) over a previous Almohad construction. Nowadays the castle is fully restored, and it houses the Museum of Archaeology and History of Elche.
Castillo de Santa Pola
A castle-fortress of the Renaissance (16th century) in the village of Santa Pola. Its main features are: two bulwarks (bulwark of the King and Bulwark of the Duke), water tank, parade ground, church, and also houses the Museum of the Sea and Fisheries.
Castillo de Onil
Abu Zayd’s old castle, King of Valencia converted to Christianity and vassal of Jaime I. Took the town in 1244. In its early days had an outer ditch, which was subsequently removed to change the function that the castle served. It has a rectangular plan, with a central courtyard and a cloister made of arches.
Some nice places in the zone that you can stay in:
http://www.escapadarural.com/casa-rural/alicante/balcon-de-biar
http://www.escapadarural.com/casa-rural/alicante/los-dos-tilos
http://www.escapadarural.com/casa-rural/alicante/la-facana