Castle Palacio de San Telmo in Seville

You're standing at the Palace of San Telmo in Seville. These days it's the seat of the president of Andalusia's regional government. But it started life as something very different. Construction began in 1682, outside the city walls back then, on a school for navigators. Orphaned children were educated here and trained to become sailors. Fun detail: the land belonged to the tribunal of the Inquisition.