In the planning stages for a fall trip to Northern Poland then flying into Budapest for 4 or 5 days. This will be our second time in Budapest, so looking for suggestions for some hidden gems or day trips.
Mister E will be along later for better help. But in the meantime, you can take a look at his suggestions on these threads. And as for hidden gems? What have you already seen/done?
https://community.ricksteves.com/travel-forum/hungary/planning-my-hungary-trip
https://community.ricksteves.com/travel-forum/hungary/private-tour-guide-for-countryside
https://community.ricksteves.com/travel-forum/hungary/5-extra-nights-in-hungary
I sent you a link with some information and ideas about somewhat unusual things in town
Otherwise for a day trip Szentendre or Vac are the two obvious options. I do know a young lady that can take you to a winery outside of town, maybe two. Makes for a good day. Pannonhalma is possible in a day. Also check the Viator site for Budapest .... not that you use Viator, but if you see an itinerary your like let me know and maybe I know the source you can deal with directly (or use viator, they really arent bad).
I always enjoy a few hours in Szentendre, very easy 45 minute trip via HEV from Budapest. I also enjoyed a long day trip to Pecs via train, arrived around 10 am and left at 5:30. Easy to walk to the main area of this pretty town, lots to explore and I particularly liked the Zsolnay museum and the ones devoted to the art of Vasarely and Csontvary, plenty of time for lunch in the main square and a stop at their shopping mall because I needed a pair of sneakers. Another trip I took the train to Tata, the charming town my family came from--this is better done with a car as there's a lot to see outside the main area and old town...very little if any English spoken, highlight was finding a few Katonas in the cemetery. There's also Godollo to tour the palace that Empress Sisi especially loved--about 45 minutes via HEV from Budapest, very easy trip for a morning or afternoon.
I have also done a long day trip to Vienna--I've stayed there twice for several days, and this was part of a solid week in Budapest--I just wanted to ride the Riesenrad and have some grossmutterschnitzel at a restaurant I love in the Prater and visit an exhibit at the Belvedere.