Rotterdam+The Hague in one day?

Once in Rotterdam, I hope you will take a river boat to visit Kinderdijk, 19 historic windmills in their original locations. Since you’re staying in Delft, you can take a tram to nearby Delft. Why not go to Delft another day?

I've heard a lot about that place with the windmills. World Heritage site.

I'm staying 3 nights in Delft. On the first day, on the way from Haarlem to Delft, I was thinking of stopping off in Leiden for a few hours. The next two days were going to be set aside for The Hague and Rotterdam but there's a big (the biggest) record fair going on in Den Bosch that weekend. This is why I'm trying to squeeze The Hague and Rotterdam into one day. I thought of combining Rotterdam and Den Bosch but they seem to be far apart (by Netherlands standards).
I could save Rotterdam for another day: a couple of weeks later when I'm planning to travel from Brussels to Amsterdam. That train stops in Rotterdam on the way to Amsterdam.

It's a very good waterbus service from the centre of Rotterdam to the windmills, fast and frequent and nice boats. Most of the boats continue to Dordrecht afterwards.
If you're so minded you can then get a train back from Dordrecht, rather than going back to Rotterdam on the train.
There is a metro stop right outside the waterbus pier at Rotterdam, with a metro from the Hague, as an alternative to NS..

Your plans are very ambitious. I spent a whole day in Leiden (sleeping in Amsterdam) and could not see it all. Your two objectives each need a full day.

Aren't the museums closed on Mondays?

I thought the museums were closed on Monday but apparently not. Mauritshuis is open from 1-6 on Mondays.
Thanks for the info about needed cash at the Den Bosch fair. And thanks to the others for the advice. I'm finding this trip a bit difficult to plan because of some of the museums requiring reservations.

One more question... I understand it's not ideal, but if you had to combine two of these three cities in one day: Leiden, The Hague, and Rotterdam, which two would you choose?

You're lucky - The Girl with the Pearl Earring will be back in the Mauritshuis by the end of March. Are you going to Amsterdam at all? The amazing Vermeer exhibit is there and I think there are still some tickets available. It's killing me that I cannot get to it (although at least I to the Mauritshuis in 2018). :)

One more question... I understand it's not ideal, but if you had to combine two of these three cities in one day: Leiden, The Hague, and Rotterdam, which two would you choose?

I have not been to Rotterdam, but I absolutely LOVED Leiden. I wish I could have gone there for longer than a day trip. It has beautiful architecture, lovely walks and is very welcoming. I really enjoyed my time there.

With regards to the Hague, I enjoyed seeing the Mauritshuis and also found time to wander around the other places, but I wouldn't say it was a "must-see" for me (a bit ironic since I did visit there). :)

“ Aren't the museums closed on Mondays?”

What museums do you believe are closed on Mondays?
The major museums in the Netherlands (Rijksmuseum, Van Gogh museum, Mauritshuis, Anne Frank house etc etc) are open every single day of the week, 365 days per year, including Christmas Day and New Year. The only exception to this rule is the Anne Frank House which is closed 1 day of the year on Yom Kippur.

The amazing Vermeer exhibit is there and I think there are still some tickets available

Nope, all gone ... so are the Friends passes ... so if you don't have tickets yet, you'd have to get them from someone who has them and can't attend.

In 2018, we took morning train from Amsterdam to The Hauge. Left luggage at the station and went to Madurodam first. Spent at least 3 hours there, maybe longer. I found it fascinating and probably would have stayed longer if alone. Then went to Mauritshuis. After that took train to Rotterdam. Arrived around 5 pm to stay the night. (Went to Euromast tower before sunset.) Next day went to Kinderdijk by water bus. The windmills cover a fairly large area, so walking to each takes time. Two were open to go into. Took water taxi back to Rotterdam and did the RS walk route, and I think took most of the afternoon. Toured the Cube House on the route. Stayed second night in Rotterdam.

In my opinion, you would be too rushed to do the four things you listed in one day.

Yes, Lynn, I think I would be too rushed to try and fit all these places in two days. Thanks for your advice.
And thanks to Tim... another voice of reason.

Sounds like I can see Madorodam and Mauritshuis in one day at least.
Yes, Mardee, I am going to Amsterdam and I did manage to score a reservation for the Vermeer show.
From what you guys are telling me about my 3 days in Delft, I've definitely got too much on my plate. Gonna have to be less ambitious for sure.

Dankjewel!