Once your are in Zagreb, It is easy to make a quick excursion to Varaždin – a small city where time seems to have come to a standstill sometime in the Baroque period – and spend some time exploring its various charms. Its city-centre area is full of buildings dating from the aforementioned era for you to see as you walk around.
Medieval art enthusiasts, such as myself, will be particularly taken with the imposing castle in the old town (Stari Grad), with its immaculate walls that look as if they were just painted the day before. You can also visit the city museum housed inside it. A few hours are all you need to explore Varaždin. This will give you time to visit its main central square, stroll around its quiet streets, and even sample some of the local specialities in one of the city's restaurants (I particularly recommend the Palatin).
It is possible to extend a visit to this region of Croatia by also taking in some of the other local small towns and villages while here; with Trakošćan Castle, in particular, a particularly notable attraction in the area.