Seville is Andalucía at its very best, especially the colors - orange trees, very purple jacaranda trees, some unknown red trees (with fluffy flowers) you name it! So spring is probably the best time to visit.
Seville's cathedral is officially the biggest (in Gothic architecture) in the world: climb up to the belfry of the Giralda (1198), it's actually very easy to do, as there are no steps but just ramps (back in old times the sultan himself used to ride up on horseback!). Next to the cathedral is the Moorish Alcázar (10th cent.) with patios and garden - look for a gorgeous peacock, be patient and wait until he begins courting his "second half" (she actually looks pretty ugly), it's a real entertainment!
Visit the city's most glorious mansion - Casa de Pilatos and look for Jusepe Rubera's painting "The bearded woman" (1631). I bet you have never seen anything like that!
Avoid the Santa Cruz Jewish quarter in summer - there is nothing Jewish left in fact and it's way too overcrowded.

You are in Andalucía so why not to try the salmorejo (cold and thick as sour-cream) soup, it's served with strips of jámon (pork) sprinkled over the top. I am a vegetarian, so I just (easily) picked them up and ate my soup. It was delicious! For people not on weight watchers list I'd recommend the garlic prawns at Casa Tomate (Calle Mateos Gago, 24) but beware they are literally boiling in oil (and spicy too)!. If you are not very hungry order just one racione (12 euro) for two.
I'd personally recommend the aubergines in honey at Los Coloniales. Never mind if waitress says "Mucho, mucho" (too much), no it's not. Order a full portion and enjoy it, followed by Spanish famous tinto naranjo vino - dark orange wine.

We stayed at hotel "Petit Palace Canalejos Sevilla" (Canalejos 2) - each room has a laptop and you get a free bike as well. It's well worth it as Seville is a very bike-friendly city!
Courting in progress!
In Alcazar's gardens
The Bearded Woman by Jusepe Rubera, 1631
City full of colours
The peacock - the pride of Alcázar
The girl with oranges
This church is a good match to the city's colours
Famous azulejo benches
The Mushrooms, 2011 (the biggest wooden structure in the world)
Just a house