Zagreb Hilites

It really depends on what you like. Zagreb has lots of small and unique museums. We visited the Museum of Naïve Art, and really enjoyed it. There is also the Museum of Broken Relationships, which we didn't have time to see, but I know that people like it. And other museums, too. We spent 2 nights in Zagreb, and in addition to the Museum of Naïve Art, we spent a lot of time just wandering around the Old Town. There is a lower level and upper level. We also enjoyed the huge market, which is held every day. And there is a nice cathedral, too. We really like Zagreb. Not sure where else you are going in Croatia, but Zagreb is very different from Split and Dubrovnik, so it's a nice contrast to the coastal cities.

Must see in Zagreb - Zagreb's Upper town features some of the Zagreb top attractions: the Lotrscak tower, Stone gate (Kamenita vrata), St. Marc Church, Museum of Broken relationship, Stross promenade, the Mestrovic Atelier, and the Klovicevi Dvori gallery.

Yes, lots of art museums: some small, single-artist, museums, mostly in the historic area, and some larger museums located between the historic area and the train station. And the historic area is highly walkable, though you have to deal with the level change. There's a funicular, but there are still steps to be negotiated at the top. I'm sure there are buses that wind their way up.

In 2015 the tourist office had a brochure describing all the local museums available upon request. I found it very handy for deciding which ones I most wanted to see.

October can be coolish and rainy in that part of Europe. Be sure you have adequate outer clothing.

It’s a small city but has a few good museums, wonderful Churches, and an Upper and Lower town. There is a small funicular you can take between the two, or just walk. There is a large market outside but it is mostly food and an indoor market. We have been there a few times and it is one of those cities where you just wander around and stop in when you see someplace interesting. Of course, you can just type in Zagreb for websites or go to infozagreb.hr.

I agree with everything already said. Zagreb Upper town is the historical centre offering many interesting churches, palaces and museums. Dolac market is also a must-see as it has products from all over Croatia therefore can be a nice way to get to know the local food and life as well (it is one of the favorite places among locals). Zagreb Green Horseshoe in the Lower town is a series of impressive squares and parks with the most representative 19th and 20th century buildings (Art Pavilion, Croatian Academy of Arts and Sciences, Modern Gallery, Croatian National Theater, State Archives...) and it is perfect for a leisure walk.
If you are looking for something out of the city centre Maksimir Park to the east or Jarun lake to the west are nice getaways (both easy to reach by tram).

If you are there on Sat, there is a great flea market at Britanski Trg W on Ilica St. We stopped in, and found many things of interest - commie-era military pins, pictures, plates. We bought a picture of a deer on a board for 50 Kuna.