There are many things to see in Pamplona as it is a city rich in both architectural and cultural heritage.
Religious attractions in Pamplona include the Catedral de Santa María la Real, the most complete cathedral complex in Spain. In addition to this church, cloister, and vestry, the chancery, refectory, chapter, and bedroom are also preserved, and a tour around the complex should be at the top of the list of stuff to do in Pamplona. The cloister is considered a marvel of European Gothic art.
You should also visit San Saturnino Church, a religious Catholic building in the Old Quarter of the city that attracts thousands of tourists each year and is one of the many Pamplona attractions.
If looking for what to do in Pamplona regarding civil architecture, one of the most famous places to visit in Pamplona is the Citadel or New Castle. It's a Renaissance fortification that was formerly used by the military, and was built between the sixteenth and seventeenth centuries. Much of it is used as a garden and for cultural activities. Also relevant Pamplona activities are a visit to the Plaza del Castillo, located in the city center, which is considered the "living room" of Pamplona, and the House Comptos of Navarra, one of the most iconic things to do in Pamplona.