Salamanca is certainly the most elegant and glamorous of all the historic city centres on the Spanish World Heritage List. This is mainly due to its harmonious townscape. Almost all the historic buildings are made of the golden-yellow sandstone from the nearby village of Villamyor. And the Plateresque style of many buildings also contributes to the extravagant look of the city. Plateresque means the elaborate and detailed ornamentation that is applied to the façades, mostly to decorate the main portal. Salamanca is a hotspot of this late Gothic/early Renaissance style, you will find it everywhere in the historic centre. The façades of the University and the Catedral Nueva are two of the best examples.

The most important historic buildings are located along an axis between the Roman Bridge and the Plaza Mayor. I had accommodation south of the city centre, just outside the core zone, so I entered the old town via the Roman Bridge. From there you have a nice first view of Salamanca and the two cathedrals (photo), the Catedral Nueva and the Catedral Vieja. But rather than two separate buildings, the new and larger cathedral was attached to the old one and the two structures merged into one. Both are worth visiting. Construction of the New Cathedral began in the 16th century and was completed in the 18th century. And thus, the interior is a mixture of styles from that period: Gothic, Renaissance and Baroque. But I enjoyed the medieval atmosphere of the old cathedral more, I especially liked the tombs and wall paintings in the transept and the Capilla de San Martín.
The second attraction is just around the corner from the cathedral, the University of Salamanca, or rather the Escuelas Mayores, the oldest building of the oldest university in Spain. Before entering the building, take a look at the Plateresque facade. Binoculars or the telephoto lens are useful here. Try to spot the frog on the skull. It is said that a student who finds the frog without help will pass all exams. The frog, however, is quite small and well hidden amidst all the ornaments and figures on the façade. But as a tourist you can get help without risk, for example from this website (further down the page is also a description of strange carvings on the cathedral).
Today the Escuelas Mayores are a museum. A visit to the historic rooms, the assembly hall and the cloister is interesting but not overwhelming. Most impressive is the wooden interior of the old library, but it is closed to visitors. You can see it only from the entrance through a glass door.
And you shouldn't miss the Escuelas Menores, located in the southwest corner of the Patio de Escuelas. In one room of the nice courtyard, you will find the Cielo de Salamanca (Sky of Salamanca), a wonderful wall painting from the 15th century.

Salamanca is different, not like the winding labyrinth of Toledo and not like the austere Avila. Here the streets are wide and every few steps you come to a small square. It is great fun to stroll through the old town and explore the details of the Plateresque façades. The most striking building is the Casa de las Conchas, which is decorated with more than 300 shells. It looks different at any time of day, depending on the position of the sun, the shells create a different shadow pattern. Across the street is La Clerecía, the church of the Pontifical University. You can climb the towers for a nice view of the cathedral and the old town.
The last must-see is the Plaza Mayor. Many consider it the most beautiful square in Spain, and I wouldn't disagree. It's perfect for a break between sightseeing, drinking coffee and people-watching. And for tapas and wine in the evening, when the square is illuminatedp and the façades glow golden. Or go to the Mercado Central next door, where you can taste the local delicacies.

You haven't had enough of the Plateresque style yet?
Go to the Convento de San Esteban. Its portal is even more lavishly decorated than that of the cathedral.

You have had enough of the Plateresque style? You want to see something different?
Go to the Casal de Lis. It is the only modernist palazzo in Salamanca. It houses the Museo de Art Nouveau y Art Déco. The collection is worth seeing, but the most impressive feature is the glass roof in the patio.

I visited Salamanca in May 2019 on my trip through central Spain. Salamanca is about 200 kilometres east of Madrid, too far for a day trip. I would definitely recommend spending more time in Salamanca and also staying overnight.