My friends reply. As you'll gather she likes a bit of art.
"OK, some of my fave places to visit:
Museo Sorolla
Exhibitions on the ground floor of the Biblioteca Nacional (National Library)
Exhibitions at the Palacio de Gaviria
Exhibitions at the Sala Alcalá 31
Exhibitions at the Espacio Fundación Telefónica
Exhibitions at the Fundación Mapfre
Exhibitions at the Círculo de Bellas Artes
Exhibitions at CaixaForum Madrid
Museo de las Américas
Exhibitions at Casa Árabe
Museo Cerralbo (mind-boggling palace of a family with far more money than taste)
Museo del Romanticismo (often has fab exhibitions, but the house itself is worth a visit, as is its walled garden café)
Exhibitions at Centro Cultural Conde Duque (and the building itself, a baroque barracks)
Nearby is the stunning Convento de las Comendadoras de Santiago — occasionally open for guided tours
Exhibitions & music at Fundación Canal
See what events are on at the Ateneo de Madrid
Catch a concert at the Auditorio Nacional main hall and at the Teatro Real
Check out exhibitions at the Centro Sefarad-Israel
Walk thru the Retiro park & check out any exhibitions at the Palacio de Cristal
Check out the Plaza Mayor & Chocolatería San Ginés & the nearby church of San Ginés (almost always open)
tbh the planned list (Prado, etc.) seems a bit dry and dull, and about as far removed as possible from the modern, dynamic, creative Madrid that I know."
That's you marked as an old fogey Reg !
I'd second bhoot's recommendation for the Atocha station, lots of turtles (?) in the pools.