Hi! I studied abroad in Seville last year (and visited Barcelona and Lisbon). Seville is an absolutely wonderful city, you are going to adore it! My reccomendations would be:
The Cathedral, its the 5th largest in the world and is absolutely gorgeous. The cathedral also has La Giralda which is basically a gaint famous bell tower. But you can walk up to the top of La Giralda and see panoramic views of the city, the hills and el Guadalquivir (the river).
El Alcazár, this is the royal palace of Sevilla. The royal family stays here when they are in the city still today. It has a mixture of different architecture, and in the back there is a GIANT garden that has a labyrinth, as well as the queens baths (bath house under the actual building)
El Torre del Oro, it used to be a watchtower (13th century) and now its open for tours. I didn’t actually go inside it when I was there, but I heard good things about it. Also its right on the river so you can’t really miss it.
Metropol Parasol, this is a tri-layer crazy building that looks (to me) like a giant mushroom. It was being built while I was there, and we got to watch its progress and the final product is amazing! the bottom floor has excavations so you can see ruins from the old city below you, the second floor is a market, and if you go to the top there is a long walkway and you can see the whole city. I didn’t get the chance to to up to the top or the market because it opened right before I left, but I did see in the bottom floor and its amazing!
Plaza de España, this giant plaza is a big half circle right next to the Parque de María Louisa (also amazing) that features little alcoves with colorful painted tile representing differnt cities in Spain (hence the name Plaza de España) It also has a small moat(?) type deal that runs through it with boats that you can ride on, and a giant fountain in the middle. In the summer, this is where lots of the street vendors set up shop with hand painted spanish fans and other trinkets
Parque de María Louisa which is right next to La Plaza de España is an amazing place to be. It is full of different buildings, sculptures, art, there is a muesum or two, I highly recommend spending an afternoon wandering through here.
Triana/Los Remedios: These are the two main neighborhoods in the center of the city. They are right across the Guadalquivir river and are worth a look. I would reccomend walking across La Puente de Isabel II/Puente de Triana (the bridge with the circles on it) and visit San Jacinto. San Jacinto is a street with different shops and places to look at, but while you’re on that side of the river it is a must to check out the pottery of Triana. If you go over the bridge and turn right, you will end up in some windey streets that are full of pottery places which Triana is known for.
Plaza del Toro: The bull fighting ring, although its a very controversial sport in Spain, its still cool to go on the tour of the ring
Universidad de Sevilla, I don’t know if you know anything about Carmen, but this is where the newest movie was filmed. Mostly I love it because its an amazing building that was transformed from a tobacco factory into a university, and its where I took my classes (well half of them)
Food: Tapas all the way! Some of the good places I ate at were:
Rayas: this is an ice cream shop, and I know it sounds silly but it has the BEST and I mean the best ice cream. If you’re in Sevilla its definitely worth a stop
T de Triana (best Tapas AND flamenco)
El Giradillo (tapas)
T de Triana (tapas and flamenco, what more could you want?!)
La Carbonería (kind of hard to find but TOTALLY worth it)
FINALLY! Since you’re going on your honeymoon to Sevilla, it is only natural to put your lock on the bridge. What I mean is, when people (especially couples) go to visit Sevilla, they buy (or bring) a padlock with them to write their names and the date on and then lock it to the bridge to represent your love. When I studied there, a lot of the students (including myself) put our locks on the bridge to show our love for the city :), basically just a fun little thing to do before you leave.
Sorry if this is a ton of information, I’m just really passionate about Sevilla. I spent about 6 months there and I would love to go back. I figured since you got so much information about Barcelona, I would chime in with some Sevilla info! Have fun! You’re going to love it.