I call it old town Pamplona to distinguish it as the area with the bull run and the original centre of Pamplona opposed to the newly developed areas with hotels, businesses, shops and malls.
For someone unfamiliar with the town, I will tell you without hesitation that Old Town is difficult to navigate without a map. It's not that the town is big. It's quite small. You could probably have a stroll by foot through the main areas in one day. The issue is the layout of the town...
Normally, we are often used to towns that are designed based on a square grid where streets run parallel. You know if at one point you were on street A and it was parallel to street B, that some time later if you were further down on street A that its still likely to be parallel to street B. But in Pamplona because the streets are curved, if you're on street A trying to go to Street B, you may not get there by going the same direction you would have gone before. A number of times, I have depended on my memory and this theory, but I ended up lost so many times. Make sure you print out a map of old town Pamplona, or get a copy of the map from your hotel.
You might get the impression that all of old town Pamplona is a huge party during San Fermin (Running of the Bulls). Estafeta is the busiest street in all of Pamplona. Surrounding Plazas (squares such as Plaza Del Castillo) will also be quite busy. However, the truth is surrounding streets and avenues will not be as crowded and can sometimes even be near alienated. It's good to know this because this will help in decided where to find a hotel, and it's good to know, there are some streets and restaurants and lookout points you can peruse without all the crowds and noise.
Estafeta During San Fermin
Another Random Street During San Fermin
Any questions? Please post your questions in the comments area, and I will be happy to answer you.