The topic of this tentative site is not University of Bologna, the oldest operating university in Europe, or Historic Centre of Bologna, one of the largest historic centres in Italy. The title is The Porticoes of Bologna. The nomination picks out one architectural element and focuses exclusively on it. The historic city centre is only the buffer zone of the nominated property, and the core zone does not even consist of whole buildings. Actually only the porticos are included. Really a strange nomination.
Porticos are everywhere in Bologna. In the city centre, they stretch over a length of almost 40 kilometres, more if you include the outskirts. However, not the entire network is nominated. Twelve locations were selected to represent 900 years of architectural evolution, from the 12th to the 20th century. About half of them are located in the city centre, so that every visitor to Bologna can safely tick this site as properly visited if it will be inscribed.

Update August 2021: The nomination has changed following the evaluation by ICOMOS. The inscribed areas have been considerably expanded to include not only the porticoes but also the associated buildings and additional components such as Piazza Maggiore and the Basilica, Palazzo Poggi, Cimitero della Certosa, the entire Church of San Luca, etc.

I have visited Bologna several times in the last decades, two visits were after 2006 when the porticoes became the topic of the TWHS. Based on my memories and confirmed by my photos, I can conclude that I have visited at least eight of the twelve locations.

The Portico del Pavaglione (photo left) is located right in the heart of the old town, on the east side of Piazza Maggiore, along the Basilica di San Petrone to Piazza Galvani. Essentially it is the porticos of the Palazzo Banchi and the Palazzo dell'Archiginnasio. The latter was once the main building of the university, today it houses the municipal library. Most tourists come to see the historical Anatomical Theatre.
Just around the corner is Piazza Cavour e Via Farini. The layout of the square dates back to the 19th century, when the area became a banking district. Today you can find the high-fashion brands here that perfectly match the elegant porticos with colourfully decorated ceilings (middle photo).  
The triangular Piazza Santo Stefano is one of the most beautiful spots in Bologna, wonderful for an espresso in the morning or a glass of wine in the evening. You are surrounded by façades and porticos from the Renaissance.
One of the longest stretches among the twelve parts is Strada Maggiore, which begins at Porta Maggiore and ends at the two leaning towers Asinelli and Garisenda, the city's landmarks. Most notable here are the porticos of the Basilica of Santa Maria dei Servi and its churchyard, as well as the Casa Isolani from the 13th century with a high wooden portico on which the third floor rests.

Two other components are in the northern part of the medieval city. Via Galliera was once the main access road to the city centre from the north and is flanked by noble palazzi and porticos. And Via Zamboni in the university district: the nominated section consists mainly of the porticos of the Palazzo Poggi complex, the headquarters of the university. The University Museum is also located in Palazzo Poggi and is highly recommended for everyone who is interested in the history of science.

I also walked along the Portico di San Luca (photo right) up to the Sanctuary of the Blessed Virgin. It has a length of almost 4 kilometres and is considered the longest covered walkway in the world. However, you can skip the first part and take a bus directly to the Arco de Meloncello, where the nominated section begins. When it was built in the 17th and 18th centuries, the entire portico was outside the city walls, but later residential houses were added along Via Saragossa and today you walk along shops and bars. Maybe these changes are the reason why only the uphill stretch is included. It is quite steep in some parts and I’ve seen a lot more runners than real pilgrims. [update August 2021: The revised nomination now includes the entire section from Porta Saragossa to the Church of San Luca.] 

By chance I also visited the Via Santa Caterina component. In 2013, I went to Osteria Santa Caterina for dinner, a recommendation from a colleague. It is an ordinary neighbourhood, workers and craftsmen used to live here. The porticos are low, narrow and undecorated, but often the old wooden beams are still visible. I was surprised to find this section on the list of nominated components.
The other four components are on the outskirts of Bologna, including the most recent part: a porticoed building in the Barca district as an example of urban expansion after WWII.

I like Bologna. It is a vibrant city with a good mix of locals, students, and visitors, not crowded with tourists like many other places in Italy. Bologna is rich in culture and history and not to forget the excellent cuisine. Tortellini and Mortadella come from here, and the original Ragù alla Bolognese, to name just a few local specialties.
I like Bologna, but I don't like this nomination. Porticos or arcades or colonnades (whatever the exact difference is) can be found all over the world. They are so common that we don't even have a connection for them on this website. There would be too many. Well, nowhere are there as many as in Bologna, neither in Italy nor elsewhere in the world. But is that enough for a WHS? Does it really make sense to evaluate the evolution of an architectural element separately from the historical and cultural significance of the associated buildings?
All in all, a thumbs down from me. But we will have to wait and see how the WHC deals with it. Perhaps Bologna will remain one of my top non-WHS destinations in Europe.
Update August 2021: Finally, a revised and improved nomination was inscribed at the WHC 2021.