I didn't actually go, but the pictures I have seen of the bridges look spectacular by night.
The island houses both gothic and renaissance styles and you can visit the Carthusian order of Saint Mary of the Caves.
Monasterio de Santa María de las Cuevas (Monasterio de la Cartuja). The first church was built in the 16th century by Rivera, undergoing several extensions and reforms until the 18th century. it was later acquired by the Marquis of Pickman who founded crockery workshops there. It is currently host to the Andalusian centre of contemporary art. Timetable: from tuesday to saturday from 10.00 to 20.00. Sundays and holidays from 10.00 to 15.00. Free on tuesday for members of U.E