The Z.
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Used to stay there several times. Nice clean rooms, a little bit noisy, given that it is in the center of Zagreb's nightlife. Their bar is also very cool, with live music and hookas. One winter, the radiator in our room was broken, we couldn't turn it off, so we had about 30 degrees in our room, but given that it was very cold outside, we didn't mind and stayed in our room, although they offered us another one =)