Proposal in Spain

Definitely Granada, at the Alhambra. You'll probably want to arrange your trip so you are there more towards the beginning and not travelling around with a ring in your pocket (or suitcase). I think you could shave off a few days from Barcelona and fly to Granada from there. You will also need to buy your tickets to the Alhambra well in advance (months). Good luck!

I suggest making your proposal directly in front of "The Garden of Earthly Delights" in The Prado.

My only hesitation with proposing inside the Alhambra itself is that it will not be too private, many people will be there touring the palace.

I was thinking that you could propose on the hill opposite of the Alhambra, with the view of the Alhambra with Sierra Nevada in the back drop, my pick would Mirador de San Nicolas. If you get there early in the morning I think that you could avoid most of the people.

I think that the Bunkers del Carmel might be a good option too, with some spectacular views of the city, however it has a more gritty and urban feel.

If you would like more nature and privacy in Barcelona, then I would recommend Parque del Laberinto de Horta. It's 18th-century neoclassical garden on a former palatial estate. It's not very well known with tourists so you will probably have a more private setting. It's very beautiful with numerous sculptures of Greco-Roman mythology along with a number of fountains, springs, and pools. In the center of the gardens is an English style hedge maze.

If you would like privacy, nature, and neoclassical architecture in Barcelona my pick would be Parque del Laberinto. Although, I should say that it may not be as impressive in the winter as it is in the spring/summer. Hope this helps :)

Wouldn’t it make the trip more celebratory if you propose at the beginning? Thinking of Barcelona, perhaps at the top of Mountjuic with the whole city below?

I'd agree with Carlos: the Mirador de San Nicolas would be ideal. It's a really lovely view, and if you go in the morning, I think you'll have all the privacy you want. Hopefully you'll get decent weather - in February, the mountains in the background should be strikingly beautiful and covered with snow. Bring some warm cloths and layers!

I have been to all of those locations except Barcelona, but my first thoughts are the same as Suki. Aim for the proposal to be halfway through your time in Barcelona. As a romantic, I would appreciate it being at a city where we would still be for a couple of days. Also thinking that if you have a couple of mishaps during the trip, she will tend to overlook them because it’s your proposal vacation. And, you won’t have to worry about guarding the hidden location of the ring in your suitcase so long. Congratulations!

Definitely agree with Suki and Jean -- the place of the proposal is way less important than the event itself, and then the rest of the trip can be magical because you are engaged. Less strain on you to keep the ring hidden -- and maybe less strain on her if she's wondering at each dinner "Will he do it now ?"

No "Garden of Earthly Delights", please, though I suspect that was a joke. That's one of the two paintings in the entire Prado that had a sizable knot of people in it every time I walked through that room during my 2015 visit--and the museum was not at all busy that day.

As for trimming the 7.5 days allotted to Barcelona--heresy! The OP is an architecture fan! I'd be tempted to trim time off Madrid and increase Toledo to two nights. And I'd recommend a side-trip to Segovia, which has some interesting architecture.

Many beautiful spots to choose among. I’ll be a tad practical. If you are absolutely sure she will say yes, then certainly ask near the beginning of your trip, and celebrate throughout. If not absolutely sure, you might want to enjoy a wonderful and very compatible trip, then pop the question near the end, just in case. Good luck!

To Larry's suggestion, I am reminded of the advice given to new trial lawyers "never ask a question unless you're sure of the answer."

Make sure to put the ring in a money belt (pickpockets) but how you gonna the ring out ?

If you can arrange your schedule to be in Granada for a night visit to the Nasrid Palaces, the far end of the courtyard with the large reflecting pool is a perfect place. Other than the Alhambra, I don't think Granada is particularly beautiful.

The Garden of Earthly Delights is not exactly romantic - I was so impressed with it, I bought a poster and had it framed. It hangs in a prominent place and I look at it often.

In Sevilla, you could hire a carriage and do it in the late evening, by the beautiful cathedral. Or maybe first thing in the morning in the Alcazar, if you make a beeline for the gardens, they should be nearly empty.

I guess I find Andalucia more romantic than Barcelona. I do remember the cloisters of the cathedral in Girona (day trip from Barcelona) being pretty quiet and somewhat charming. I'm sure Enric can recommend cloisters in Barcelona that are at least as good a location.

Thanks everyone for your amazing suggestions! I do think that doing it near the beginning of the trip is a good point (I'm pretty sure she'll say yes), but that basically limits me to Barcelona and probably Granada.

Yes my concern on Alhambra is the amount of tourist, I did had the idea of staying a night at Parador de Granada and do it at night since it is part of Alhambra. But it seems that the hotel has mixed reviews so I filtered out the idea.

Mirador de San Nicolas suggested by Carlos looks amazing, it is much more romantic than an ex-war bunker I suppose. I will do it there during sunrise if I choose to do it in Granada instead of Barcelona.

I did thought about Parque del Laberinto before coming up with Bunkers del Carmel but some videos on youtube has children running around so I'm a little worried that would ruin the romance during the proposal.

Carriage in Seville at night sounds very romantic, I'd definitely do it if Seville is the first or second city I go in Spain, but currently Seville is after Granada so I might not be able to do that.

Thanks everyone again for all of your suggestions, it is a very important life event for me and I really appreciate your help!

P/S if I really were to do it in front of an art piece it would be Bernini's Ecstasy of Saint Teresa or Romans in their Decadence in Orsay Museum. (I wanted to say Apollo and Daphne at first but it's weirdly inappropriate in this context.)

Recently, a friend of my son - proposed in Sevilla at the Plaza de Espana. His bride-to-be was delighted. Your girlfriend will be delighted no matter where you propose. Check out some google images.

Your girlfriend will be delighted no matter where you propose

Indeed, I proposed in Prague, was intending to do it somewhere impressive but ended up proposing in our hotel room as the moment felt right! It turns out the location was unimportant, it was the gesture that counts.