There are many places to visit in Oviedo, especially those related to the so-called Asturian pre-Romanesque art, which developed during the existence of that kingdom in the ninth and tenth centuries.
Examples of this art, which are also major attractions in Oviedo, are the Holy Chamber, a chapel located within the architectural complex of the Cathedral; and the wall of San Tirso or Foncalada, one of the top things to see in Oviedo that houses a fountain. The latter is the only conserved civil Romanesque work of art.
In terms of religious architecture, Oviedo attractions include the Cathedral of San Salvador, a mainly Gothic building built between the fourteenth and sixteenth centuries, the Monastery of San Vicente, the Monastery of San Pelayo, the Church of San Isidoro, built by the Jesuits in the seventeenth century, and the Church of San Juan el Real, all of which should be on your list of what to do in Oviedo.
Other of things to do in Oviedo include visiting the numerous palaces, like the Valdecarzana-Heredia Palace, the Palace of Malleza-Toreno, the Camposagrado Palace, the Palacio del Marqués de San Feliz, and the Palacio de Velarde. Visiting the latter is one of the necessary Oviedo activities. More stuff to do in Oviedo can include a cultural tour and visits to museums and parks. Plan your trip well and don't leave a single corner left unseen in this beautiful city.