Cordoba - a day trip, or a morning stop before going to Madrid?

When are you going and are you cool with getting around a new city in the dark (perhaps)? I think you need more than just a 'morning' stop, but you can certainly visit enroute to Madrid. Train to Madrid is ~ 2 hours, so you can even stay until 4 or 6, and get to Madrid before dinner time. The Mesquita opens for free entry 8:30 - 9:30 in the morning so that gives you time to see the other sites, wander around the old town, have a saunter across the bridge to have lunch in the Section Sur and still get to Madrid in good time.
The train station doesn't have luggage storage, but the bus station next door to it does. About 30-40 lockers.

I love Cordoba. It was my favorite city on my recent trip to Andalusia, Toledo and Madrid. I stayed two nights. I think people that are day tripping miss a lot because there is a lot more to Cordoba than the Mezquita, and Cordoba is so beautiful and peaceful in the morning and late afternoon/evening when the day trippers have left. I can't imagine Cordoba as a morning stop. You will need to store your luggage (It is my understanding that there is luggage storage at the BUS station near the train station) and then make your way to the Mezquita. I would imagine most spend a couple hours at the Mezquita, we spent more. We didn't wait in any line for Mezquita tickets, but we were there at opening. (9am) The Jewish quarter around the Mezquita is absolutely stunning with lots of window boxes, planters and patios. Cordoba sits on a pretty river that is a bird refuge. Locals and tourists walk along the river and on the bridge for natural views and views of the Mezquita and the old town. If you are staying in Madrid for more than a day, I would consider dropping time in Madrid for Cordoba. Madrid is a fine city, lively and pretty but it doesn't have the history and interesting sights of Andalusia, especially Cordoba.

I agree with Jules. Spend an overnight trip to really get a feel for Cordoba. It's one of the gems of Andalusia and it should be explored without a rush. You will definitely have a few Kodak moments in lovely Cordoba.

Whilst I agree with others that a night or two in Cordoba is ideal, since that's not an option I prefer the idea of doing it is as day-trip from Seville. But it's just a preference and there is no "right answer" for everyone.

If you day-tripped you can catch the last train back to Sevilla, leaving well after 11 o'clock, giving you the whole evening in Cordoba and decent time for a meal there; you'd be back in Seville only just after midnight, with no luggage and time for a few nightcap since accommodation is already sorted. Carrying on to Madrid instead means leaving Cordoba earlier but still arriving (in Madrid), around midnight, but now you are still needing to check-in, leave your bags, etc. - you could still go out after, of course, but I think we'd just be lazy and decide to stay in the hotel.

Honestly, I don't think either option is terrible, I just prefer the former.

Nick, you make a good point. Should OP prepurchase the return train ticket should he choose the day trip? I'm just thinking that since its the last train of the day and on our recent trip we did have the experience of getting a train cancelled and the next train fully booked when we were leaving the COrdoba train station. Not sure if this is a frequent RENFRE occurrence or our bad luck

Depends on how much time you have in Seville. Seville itself is more interesting than Madrid or Cordoba to me, so I wouldn't want less that 3 full days in Seville.

I personally would be fine with a 3/4 day stop on the way from Madrid - take an early train, visit the Mesquita, have lunch, walk around the historic center, leave for Seville by 4-5PM, be in Seville an hour later. That gets you to Seville in plenty of time to enjoy a charming evening there (remember, dinner in Spanish cities is after 8PM at the very earliest).

Of course, if you have time then spending a night is better. But if the choice is a day trip or a stopover, do the stopover. More efficient.

Luggage - the bus station is directly across the street from the train station and it has luggage storage. I don't think you can reserve it, but if you get there on an early train you should be fine.

Thanks everyone - I appreciate all of the advice. Happy trails to you all.