Complex sentence: Oviedo is located approximately south of neighbouring cities Gijón and Avilés, which lie on the shoreline of the Bay of Biscay; its proximity to the ocean causes Oviedo to have a maritime climate, in spite of it not being located on the shoreline itself.
Split into simpler sentences: Oviedo is located approximately south of neighbouring cities Gijón and Avilés, in the shoreline of the Bay of Biscay. Its proximity to the ocean renders Oviedo to have a maritime climate, in spite of it not being located on the shoreline itself.