These cost nothing and carry a full day each. Build around them and the paid tickets become optional extras instead of a budget drain.
St Mark's Church and Markov Trg
FreeTipThe tiled roof laid in 1880 carries two coats of arms in coloured glazed tiles, the medieval arms of Croatia, Dalmatia and Slavonia on the left and the white castle of Zagreb on the right, and it is the single most photographed thing in the city. The square is free and open at all hours but the church interior is generally only accessible around Mass times, so shoot the roof between 7am and 9am before the tour groups arrive, and note that the buildings either side are the Croatian parliament and government so there is a permanent police presence and no tripods.
Lotrscak Tower and the Gric Cannon
FreeTipA cannon has been fired from the top of this thirteenth-century tower at exactly midday every single day since 1877, originally to synchronise the city's church bells, and the blast is genuinely loud enough to make first-timers jump. The tower is open Tuesday to Sunday and closed Mondays, entry is around 3 EUR, and the terrace gives the best rooftop panorama in the city, so climb the stairs by 11:45am if you want to be up there when it goes off, or stand on the Strossmayer promenade below to watch instead.
TipThe neo-Gothic cathedral on Kaptol is the tallest building in Croatia and its twin spires define the skyline, but the earthquake of 22 March 2020 snapped the top of the south spire and restoration work has kept the building wrapped in scaffolding and cranes ever since. Entry is free when the interior is open, access has changed repeatedly during the works so check on the day rather than assuming, and the medieval Glagolitic inscription on the north wall and the tomb of Cardinal Stepinac are the things to look for inside.
TipHermann Bolle designed this cemetery in the 1870s as a monumental arcade of ivy-covered domes and colonnades north of the city, and it is shared without division between Catholic, Orthodox, Muslim, Jewish and non-religious graves, which says more about Zagreb than any museum. Entry is free, it opens around 6am to 8pm in summer and 7:30am to 6pm in winter, and ZET bus 106 from the eastern side of the cathedral gets you there in about 10 minutes, so allow an hour and go on a bright morning when the light cuts through the arcades.
TipOpened to the public in 1794, Maksimir was one of the first large public parks in this part of Europe and still runs to 316 hectares of oak woodland, five artificial lakes, a mock Swiss chalet and the Vidikovac pavilion. The park itself is free and open dawn to dusk, Zagreb Zoo inside it charges separately, and trams 11 and 12 from Ban Jelacic square drop you at the gate in about 15 minutes, so pair it with a coffee at the Vidikovac terrace and allow two hours for the full loop.
Zagreb Botanical Garden
FreeTipFounded in 1889 and still run by the university's science faculty, this five-hectare garden of English-style lakes and glasshouses forms the bottom leg of the Lenuci Green Horseshoe, a short walk from the main railway station. It is closed through the winter and generally opens from around the start of April to the end of October, shuts on Mondays, and entry is a couple of euros, so treat it as a spring or autumn stop and a genuinely quiet one, since almost no visitors walk this far down the horseshoe.