My sister and I are planning a trip to Spain and Portugal together in December. Our original plan was to spend 2 days in Porto, 2 days in Lisbon, 2 days in Seville, 1 day in Cordoba, and 2 days in Madrid. After consulting a friend who has visited both countries, she has advised us we are trying to tackle too much within that time frame. Are there any suggestions on how we can get a flavor of both countries without being completely overwhelmed? We are open to changing the locations we visit but very much want to see both countries and experience as much as we possibly can during our time there.
I agree with your friend, you say you want to experience as much as possible, but by tearing around at that pace (don't forget the travel time) you wont really be experiencing very much at all.....
I tried to string both countries together in a similar frame of time, and it's hopeless. They're not well connected by trains, surprisingly, so you'd have to drive/bus or fly. And you'll be exhausted if you try. Pick one country. I'm sorry, as I'm sure you won't want to hear that, but just deciding now will save you the trouble of continuing to plan and down the road deciding it's all too much.
Ten days (do these include arrival and departure dates?) isn't much time to get a flavour of either country and transport links between the two are poor, so I would suggest that you just focus on Portugal. Fly into Lisbon for 5 nights, have 2 nights in Evora and 2 in Porto and fly home from there.
If you must see Spain, then divide your time between Lisbon then fly to Madrid and home from there. Madrid is cold in December (nearly freezing at nighttime), but I am assuming that it won't be as easy to get a direct flight home from Seville, which will be slightly warmer.
Sorry to pile on, this is not what you want to hear, but...Two things:
Start by being honest - brutally honest - with yourself about how much time you really have. You say "10 days". Many people try to fool themselves into thinking that a "10 day vacation" gets them 10 days in Europe, and that's just not true. If you're coming from North America, a 10 day trip gets you about 7 usable days in Europe. You can not/should not count either your arrival day nor your departure day, no matter what time your flights come and go. And for many folks, even the next day (the day after you arrive) you are still not at 100%, due to jet lag, exhaustion, and your body and brain's need to recover from displacement across the world. So, begin by counting the number of full, usable days you have. How many is that?
You say "2 days here, 2 days there..." That, too is an act of self-deception. You do not press a button and instantly transport yourself from one place to another. Every time you pick up and move from one base to another, you consume most of a day just with the mundane tasks of survival and transportation. Best case, if you are only going a short distance, by train, from city-center to city-center, and you are an experienced, efficient traveled (are you?) it'll consume half a day, but don't count on that. At worst, it burns almost the entire day, maybe leaving you maybe a couple hours around dinner for a cursory look around your destination. So when you say, "2 days here, 2 days there" what you really get is 1 day in those places. If you say "1 day here" you end up getting an hour or two there, not "1 day". Be honest with yourself.
All that said...10 days is too short for a trip to Europe IMHO. If this is part of a longer trip, or if you live in/near Europe, or if somehow you can go to Europe anytime and as often as you want, then ignore this part, but...the world is large. Flying to Europe from some place far away is expensive and time-consuming. Personally, I don't think it's worth going to Europe for less than 2 full weeks - the airfare cost is better applied when you can stay longer. Everyone's different, though.
Bottom line: I agree with all the above posters: your trip is too short to do what you are proposing - far too short. You need to either find a way to stay longer (a lot longer), or you need to cut down your planned itinerary (with the time you have, I'd pick 2, or a maximum of 3 well-connected places).
If that is truly all the time you have pick either Portugal or the Andalusia area of Spain knowing you won’t see nearly enough. If you go to Portugal divide your time between Lisbon with a day trip to Sintra and Porto. If you choose Spain see Sevilla with a day trip to Cordoba and Granada. Forget about Madrid unless that is where your flight departs. Even with a lot more time, trying to see Portugal and Spain together is tough given the lack of decent train connections.
My advice .... “Listen to the advice”.
Ten days is a reasonable time frame for just Andalusia with Madrid.
I'll just be person number seven to give the same advice. Your friend is right (and a true friend for not letting you have a bad visit!).
I know we in the US think of Spain and Portugal as practically one country. But the transit links between them are surprisingly skimpy and time-consuming. For instance, how were you thinking of getting from Lisbon to Seville? You can take a train and bus, a bus all the way, or fly - and any of these methods, end to end, will take much of a day.
As David says, even places that are well connected (such as Porto to Lisbon) are not connected by tele-portation, so you have to allow time for that transit as well.
Before you get attached to any itinerary, look it up on the website Rome2Rio. This website should never be relied on as the last word - you always have to double check schedules and prices with the airline, bus company, etc. But it's a great start, as well as a good way to find red flags. For instance, here's Lisbon to Seville: https://www.rome2rio.com/map/Lisbon/Seville
If it's any comfort, your issue has popped up all over the Rick Steves Travel Forum in the past few days. Here's two near-identical posts, both very recent (there are others I can't find right away):