How to spend 5 days in Netherlands in August

Please don’t take this the wrong way, but I suggest you to get a guide book about the Netherlands. You have given us very little information about yourself and your interests. From Rotterdam you can literally go anywhere in the country easily by train. You can even reach Antwerp, Belgium by direct train in just a little over an hour. So the possibilities are endless!

I have seen a lot of southern Germany ( within couple hours of heidelberg), been to Strausborg France, Rome Italy, Scotland, Northern England, London, and Zurich Switzerland. We love castles, old ruins, food, wine, hikes, countryside, boat rides, just a very diverse selection of sites and attractions. I have never been to Northern Germany, Belgium, or the Netherlands and was just wondering what are recommended must sees when you just have five days.

Obviously , go to Kinderdijk!
What time of year?
I'll attached my recent Trip Report. Perhaps you'll find some helpful info.
Safe travels!

https://community.ricksteves.com/travel-forum/trip-reports/the-netherlands-belgium-april-2024-brought-the-rain-pants-needed-the-rain-pants

Yes to the Rotterdam watertaxi to Kinderdijk! You could take a day trip to the Hague. And/or Delft. And with your husband branch out further to Ghent or Bruges.

You can take the train to Gorinchem with a change in Dordrecht. Both worthwhile places to visit outside the beaten path. From Gorinchem you can take the ferry to very charming Woudrichem and from there the ferry to one of our most famous castles: Slot Loevestein. https://www.slotloevestein.nl/en/

Worth thinking about is visiting the Maeslant Kering, a huge moveable storm surge barrier west of Rotterdam. Not easy to get to, but worth seeing a piece of hydraulic engineering that's unique in the world. https://www.maeslantkering.nl/english

Or you can take the train to Arnhem with a change in Utrecht for visiting the Dutch Open Air Museum. Utrecht is worth visiting too, with it's canals it looks a bit like Amsterdam, but much quieter. On the way to Arnhem you can hopp off there and take a later train at the same day with the same ticket. https://www.openluchtmuseum.nl/?taal=en

Thank you thank you, just the kind of suggestions I was looking for :)

this was very helpful to me as well -- thank you!

We were in Rotterdam for 6 nights in June. We took day trips to The Hague (much renovations going on in the city), Utrecht, Kinderdijk, and Gouda. Go to either Edam or Gouda for the cheese market. Edam’s is Wednesday’s and Gouda’s is on Thursdays. In Gouda visit the Cheese Experience, fun afternoon.

On previous trips we visited Haarlem, Delft, and Bruges (too long a trip for a short time). You can’t go wrong with any city.

De Haar Castle west of Utrecht is worth considering too. Not a real one, but medieval inspired like more castles from the 19th century. Easy to get to with the bus from Utrecht Centraal railway station.
https://www.kasteeldehaar.nl/english/?lang=en

I am going to make the assumption that on your day trips days you will be returning for dinner with your husband. This narrows how far from Rotterdam you will want to go on your two days. So Rotterdam itself, Kinderdijk, The Hague, Deft, Gouda, and/or Edam jump to the top of the list for me. All doable by public transport.

With your husband, I would conside two days in Amsterdam and then a third based upon the great suggestions on this thread and what is most interesting to the two of you.

If your husband is working with Dutch colleagues, rather than attending a conference, be prepared to alter you plans to spend time at a home or at an event with locals.