spain in december

We just did this itinerary in reverse. You can get to Granada in 3 hours by bus (or train, but bus is easier bc no transfer). We flew from BCN to GRX and you can do the same in reverse.

For Sevilla:
Accommodations
This is where we stayed, but I know your hotel is already set
http://www.overlandsuites.com/en/

Food
I'm sure you have read this or know, but people do not start eating dinner until 10pm! Lunch is usually 1-4pm. Many places don't even re-open for dinner until 8pm, but at the more popular places you will have a better chance of getting seated if you go closer to when they open (and definitely before 10pm). These are the places we tried and loved:

La Azotea (there is one in Mateo Gagos street that may be closer to where you are staying) - http://laazoteasevilla.com/en/restaurant-santa-cruz/

Reyes Antonio Romero - recommended by local for the Montaditos (small sandwiches - they have gluten free) - http://www.bodeguitaantonioromero.com/es/reyes-antonio-romero/

Sal Gorda - https://www.yelp.com/biz/sal-gorda-sevilla-2 - arrive early if you can. Before 10pm for sure.

La Brunilda - http://www.labrunildatapas.com/ - had lunch here. Get there right when they open or you'll wait a bit.

Petit Comite - https://www.yelp.com/biz/petit-comite-sevilla-2

We walked by Bartolomea and that looked good - sister restaurant of La Brunilda. All of these are on TripAdvisor too.

Things to do
Tapas tour
http://devoursevillefoodtours.com/

Flamenco Show
not touristy - recommended by Rick Steves
http://www.lacasadelflamencosevilla.com/

Bike Tour
This is the one we did, but there are several
http://sevillabiketour.com/

Rick Steves recommends these guys - I needed to book in advance and I didn't so we went with the one above
http://reallydiscover.com/

The Cathedral was interesting and so was the Alcazar. They are basically next to each other and have the same or similar admission prices (9 Euro). The Alcazar is free on Mondays during the last hour it is open (I think 6:30-7:30pm).

Barcelona:

Accommodations
we stayed at Hotel Gran Via in 2013
http://www.hotelgranvia.com/en/

and here this time:
https://www.aspasios.com/apartments-barcelona/rambla-catalunya-suites/

Food
Basically stay way from any place on Las Ramblas or anywhere that has pictures of menu items outside. We liked these:
Ciudad Condal - https://www.yelp.com/biz/ciudad-condal-barcelona
Xaloc  - http://www.xalocrestaurant.com/en/ (this one is the closest to your hotel)
Paco Merlago - http://www.restaurantpacomeralgo.com/the-restaurant/

Wanted to try Tapas 24, but it was too crowded every time we walked by (might be good for lunch). All are on TripAdvisor if you want to look up on that site too. The Boqueria market is good to wander around if you want to graze (just off the main drag - Las Ramblas). There are other markets as well, just didn't get to them.

Things to Do
La Sagrada Familia - book a few weeks in advance. We did the audioguide in 2013 and a guided tour this time.
http://www.sagradafamilia.org/en/

Get lost in the Barri Gotic - lots of winding streets

People watch in front of the Cathedral in the Barri Gothic to dance the Sardana (Catalan national dance) on Sundays. At noon, a crowd will just gather and start dancing.

La Pedrera (also known as Casa Mila) - they have a night visit and an option to listen to jazz on the rooftop. Did not do this but wish we did.
https://www.lapedrera.com/en/visits/la-pedrera-by-night/gaudi-pedrera-the-origins

Runner Bean Tours has several free tours - wanted to try but didn't get the chance
http://runnerbeantours.com/

The Palau - heard the concerts are great
http://www.palaumusica.cat/en

Picasso Museum
http://www.bcn.cat/museupicasso/en/museum/presentation.html
The first Sunday of every month might be free (double check). Otherwise, book tickets in advance.

I am missing a lot of things Gaudi and otherwise, but others will chime in.