Choose two of three Iberian day trips?

Sintra and Toledo. Montserrat is over-hyped.

If you go to Madrid you can't skip Toledo. It's a must see destination in Spain. On my trip to Lisbon I skipped Sintra and went to Nazare and Obidos instead.

Toldeo!!! A definite must....I have not been to Sintra or Montserrat, but from the information I have seen on line, and from personal experience, Toledo would be my choice. 1/2 hour via train from Atocha in Madrid

I agree completely with Ed: Sintra and Toledo are a must. Montserrat not so much.

I'd go further: so many people think they are going to "do Spain" in a week, and figure the must-see stops are Barcelona and Madrid, and they skip all the great things around Andalucia. This is extremely foolish, IMHO. Barcelona is a very interesting city, but it's also way far away from all the other good stuff in Spain, and having been to both (several times), if time is short, I would suggest skipping Barcelona altogether (save it for another trip) and spend those days around Madrid and/or Andalucia. I think many Americans are pretty clueless about what to see in Spain. They're heard a lot about Barcelona, but they know nothing about Granada, Sevilla, Toledo, Cordoba, the White Hill Towns, etc.

FWIW, on a recent trip with many highlights, Sintra and Toledo were among our favorite places.

If you can, make Toledo an overnight trip. It's beautiful after dark and much more peaceful without all the day trippers.

I agree with HK. We loved our overnight stay in Toledo.

Thanks for all the great advice everyone! I was 90% sure of doing an overnight in Toledo and skipping on Montserrat. As far as southern Spain goes, I hope to do that on another trip, with a 2nd visit to Mardid and perhaps even the Algarve.

Return tix have already been booked from Barcelona so not much flexibility there.