Salamanca is also named a part of the World Heritage Site by Unesco and is also the first Spanish city which ever found a university. It's a noble, picturesque city with palaces, mansions and cathedrals, which would be worth every minute of your time.
Nowadays, Salamanca is one of the cities in Spain with the most significant student society. It attracts young people from the country and abroad.
A day trip to the city is just enough, but you should take care and plan it in advance because getting there takes between two and a half and three hours, depending on your chosen means of transportation.