Lotrscak Tower and the Gric Cannon1h
Be at the Lotrscak Tower by 11:45am to climb before the Gric cannon fires at exactly midday, as it has every day since 1877, and stay on the terrace for the best rooftop panorama in Zagreb. Entry is around 3 EUR and the tower is closed on Mondays.
TipA 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.
St Mark's Church and Markov Trg30 min
Walk three minutes north to Markov trg for St Mark's Church and its 1880 tiled roof, carrying the arms of Croatia, Dalmatia and Slavonia beside the white castle of Zagreb. The square is free and open all hours, the interior generally only around Mass, and the parliament and government sit either side.
TipThe 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.
Museum of Broken Relationships1h15
Two minutes downhill on Cirilometodska, give the Museum of Broken Relationships a proper hour: donated objects from strangers worldwide, each with the story of the breakup it outlived. It opens daily and stays open into the evening, so it also works as a fallback if the weather turns.
TipZagreb's most original museum displays objects donated by strangers worldwide alongside the story of the breakup they survived, an idea that won the European Museum of the Year Kenneth Hudson Award in 2011. It is on Cirilometodska in the Upper Town, open every day (roughly 9am to 10pm in summer and 9am to 9pm the rest of the year) so it works as a rainy-afternoon or late-evening stop when everything else has shut, and entry runs around 7 EUR with a cafe next door that shares the joke.