Porto is one of my favorite cities and a relatively undiscovered European gem. My very first business trip in the telecom industry was trip to Lisbon for DSL Forum about 20 years ago, and I've been back to Portugal many times for work and personal travel since then. Porto has a charming shabby chic appeal about it; it's not the most modern of European cities, but it is one of the most atmospheric. I hope everyone coming to the DTF has an opportunity to explore a little bit and enjoy this lovely place.
I haven't tried to write any sort of definitive tourist guide to the city – there are enough travel shows and websites and guidebooks out there for anyone wanting to plan touristic activities while you're here. There are beautiful churches and museums and art – I'm just mentioning a view of the things I particularly appreciate to get you started.
Food
Food is great and affordable! This is certainly not an exhaustive list of specialties, just some of my favorites.
Barnacles: Yes, you read that right. Barnacles. They're a coastal specialty in Porto, extremely dangerous to harvest, and fun to eat. They're often served as an appetizer, and you need to extract them from their shells by peeling and twisting before you eat them. (I had a friend once who just started munching down and wondered why they didn't seem chewable or good in any way).
Alheira Sausage: Sausage made with poultry, game, and breadcrumbs. It's usually flash fried and served with a sunny-side egg on top – crispy and delicious! The historic backstory is that the Jewish population created this sausage to blend in during the Inquisition. It looked like pork sausage but didn't violate kosher laws, and some historians credit it with saving hundreds or thousands of Jewish lives in medieval times.
Caldo Verde (Green Soup): One of the most well known dishes in Portugal, it's a soup made with leafy greens and chorizo. It's very soothing.
Acorda Alentejana (Portugese bread soup): This is usually served with a poached egg on top and has a fragrant broth full of herbs. Possibly one of my favorite soups in the world.
Bacalhau (Salt Cod): Portugal has a significant sea-faring past, and dried salt cod was developed for sailors on long voyages. It remains a core dish in Portuguese cuisine with a number of different preparations. Be aware that because it's been salt-cured to preserve it, it can be fairly salty depending on how it's reconstituted and cooked.
Pasteis de Nata (Custard Pastries): These might be my favorite pastries in all the world (well except for the croissants from that bakery on Rue Mouffetard whose name I don't remember near the weekend market). It's a puff pastry case with cooked custard inside. The top may look burnt, but it's just a little bit of caramelization. Fun historical fact: these tarts originate from a monastery in Belem outside of Lisbon, where the monks and nuns used egg whites to starch their clothes and ended up with a huge number of egg yolks left over. They decided to make egg custard with all that extra fatty goodness and created the iconic pastry. In fact, you will sometimes see them called Pasteis de Belem, which means they come from that original recipe – that name can only be used by Fábrica de Pastéis de Belém which purchased the recipe from the monks when the monastery closed down.
Queijo da Serra da Estrela (Cheese from Serra da Estrela): This creamy, yummy, delectable sheep's milk cheese is so soft you scoop it out of the rind with a spoon. Try this cheese. Trust me.
Fried Sardines: Another great snack or appetizer. Don't worry – you can truly eat them whole. Just pop the fish into your mouth and enjoy the crunchy, salty happiness.
As you might notice, I love eating in Portugal. Other very typical things you'll find include numerous seafood preparations and any number of meat (usually pork) and bean dishes. Portugal also has excellent blood sausage if that's your thing. It's definitely my thing. Now is probably a time to note that Porto is not the most vegetarian of cities – in traditional restaurants, even beans and veggies will often be cooked with meat stock or fat. On the other hand, it is a sizeable town and becoming more cosmopolitan, so you should find options (a selection of starters may be your best bet in the more traditional joints).
One thing to note is that in many Portuguese restaurants, you'll encounter the "couvert." This is bread and cheese and sometimes other light appetizers that are placed on the table before you order your meal. They're often tasty and generally inexpensive, but they're NOT free. If you don't want the snacks, don't touch them, or wave the waitstaff off when they're bringing them. Just don't be shocked when you get the bill and there's a (small) charge for consuming them. And if the couvert happens to be queijo da Serra da Estrela, definitely eat it.
Azulejos (Portuguese Tiles)
One of the most iconic things about Porto is the profusion of traditional blue and white tiles on the buildings. They're absolutely stunning and you can enjoy them just walking around. There are a couple buildings that are particularly spectacular inside (the main train station comes to mind) but just seeing them on building exteriors lets you know that you're in Portugal and that life is good. If you find yourself in Lisbon before or after the event, the Tile Museum is a fascinating little joint that delves into the history and manufacture of traditional Portuguese tiles and contains a breathtaking chapel completely covered in them.
Funicular do Guindais
I'm mildly obsessed with funicular railways. I think they're engineering marvels with their counterweighted pulley systems, wonderfully picturesque, and enable you to avoid walking up and down steep hills. Porto's funicular is near the river and has some lovely views, and one of my favorite things is that it's mainly used by locals for their daily commute rather than simply being a tourist attraction. Go put the fun in funicular!
Mercado do Bolhão
Sadly this historic traditional outdoor food market is currently closed for renovations. 
Ponte de Dom Luis I
The bridge that crosses over the river to Vila Nova de Gaia (the island where the traditional port houses live – see more about this below) was designed by a student of Gustav Eiffel (yes, that Eiffel, of the iconic Tower in Paris). It's a stunner with its beautiful metal arch. There's a tram that crosses over the bridge that provides easy public transit and lovely views if you do decide to visit the port houses.
Port Houses of Vila Nova de Gaia
I highly recommend Porto's eponymous fortified wine. All the traditional port houses are on an island just across the river from Porto proper. There are port houses that give tours and in-depth explanations of the history and port-making process, and I definitely encourage you take one and learn about this beautiful elixir. The wine from which port is made is actually grown upriver in the Douro Valley and aged in and shipped from the port houses. Note that the non-fortified wine from the Douro Valley is also often excellent, especially the reds. Port tastes the way it does because it's "fortified" by adding a spirit during fermentation to halt the process leading to higher sugar and alcohol content. You've probably seen or experienced port before, and you have access to the internet and wine guides so I won't go into great detail, but here are a couple of my personal tips if you're interested:
- White port is less well known and rarely found outside Portugal. Much lighter than the typical red ports, it's generally enjoyed as an aperitif, in other words as a light drink in the late afternoon or before the meal rather than with dessert. It's totally underrated and a perfect accompaniment to some light snacks or seafood overlooking the river in the late afternoon. It makes me extremely happy. You can also find white port and tonic as a typical summer cocktail.
- Colheita – most folks are familiar with Tawny port. Colheita is a single vintage tawny port aged for at least 7 years, but often for 20 years or more in wooden barrels. It will be identified from the year it was made (much like vintage champagne) rather than its general aging time (10 year, 20 year, etc.) as tawny ports are. This is serious stuff – it's more expensive and rare than regular tawny port, but it's so worth it to try at least once.
- White colheita – you almost never see this since white port is really meant to be a light wine for summer quaffing rather than for serious aging, but on good years some port houses make a single vintage aged version of the white version. It's special; it's unusual; it's stunning.
- While there are a number of great port houses and tasting experiences, my personal favorite port is one that's less well known and rather small but also the oldest: Kopke. It only has a small tasting room, but their product is extremely high quality, and they're one of the few houses that has a deep catalogue of white colheitas. My brother the sommelier first recommended it to me, so if you don't trust my judgement, you can trust in that of a professional.
Outside Porto
If you're staying for a few days afterwards, you may want to venture further afield. There are lots of lovely spots if you're using this as an excuse to take some of your summer holidays. Below I've just noted a couple places I've been that you may find yourself wanting to visit.
One note, once you've left the Sheraton, you may want to consider staying in a pousada. Pousadas are inns or hotels in historic properties that are owned by the government – they provide a unique experience for travelers and enable properties that might have once been falling into disrepair to find new life. Many of them are in old monasteries or convents or even castles. They're unique to Portugal and well worth seeking out. You can find them both in cities and in rural areas.
Guiamaraes
This small town is about a 30-45 minute drive from Porto. It's a small medieval town whose entire historic center is a UNESCO world heritage site. It's also home to a great pousada located on a cliff overlooking the old town. If you're looking for a special experience, I recommend staying a night here: https://www.pousadas.pt/en/hotel/pousada-guimaraes.
Lisbon
More modern and bustling than Porto, the capital city is an easy train ride from Porto, and some of you may even be flying out from here. Walking along the waterfront or having some fried sardines and a glass of white wine atop one of Lisbon's many hills are delightful experiences. The tile museum I mentioned above is cool, and you can see another one of Eiffel's student's creations at the Santa Justa Elevator (it's just as it sounds, a large free standing elevator to take you to the top of one of the hills). And get this: Lisbon has not one, not two, but three separate funicular lines! It's an embarrassment of riches. San Francisco is extremely hilly and doesn't even have one funicular, and Lisbon has three! To make things confusing, they're also sometimes called elevadors, but I'm sure y'all can figure it out.
Sintra
Located a short train ride from Lisbon, Sintra is a quaint town with a number of castles and palaces to explore. If you drive to Sintra, it's not that far to the coast where you can eat at a charming cliffside restaurant and, to come full circle in my little guide, have some barnacles overlooking the ocean.