Central Croatia is the region in today's north-central Croatia, in the center of which is the capital city of Zagreb. It doesn't have a distinctive name (such as Istria or Dalmatia), and people usually know it only for its vicinity to the capital. In fact, most visitors of Zagreb never bother taking a peek outside the city, and so they miss out on a fair bit of interesting places to see and things to do.
The following counties comprise Central Croatia:
Međimurje is the northernmost county, located between the rivers Mura and Drava, about an hour's highway drive from Zagreb. It is a densely inhabited rural area, but still a rather advanced county with high employment rate. The agriculture is so customary among the residents of Međimurje that the average arable field is smaller than a single ha. Nevertheless, some of the finest Croatian wines come from Međimurje's many vineyards.
Its center is the town of Čakovec, founded in year 1333, and known for the large castle belonging to the noble Zrinski family. These days it's a busy little town with various industries (particularly textile) and various service -- not unlike the farmers, the small entrepreneurs are also found in abundance.
Named after the city of Varaždin whose first written mention dates way back to 1181 when king Bela III mentioned the county's thermal springs in a legal document. The spa, Varaždinske Toplice, is now a small town outside of Varaždin proper, and a known recreational facility.
But let's get back to the city itself: since 1209, when it was declared a free royal town by king Andrija II, the citizens and the nobility in the city's castle lived in a symbiosis, and flourished: the city became the economic and military center of the whole northern Croatia. Due to Turkish raids, the city was structured defensively, around the old fortress, and acquired the shape of a typical medieval Wasserburg.
In 1523, a count named Juraj Bradenburg built the town hall in late baroque style, which remains in place today as one of the older town halls in all of Europe. In 1756, the ban Franjo Nadasdy chose Varaždin as his official residence, and in 1767, Varaždin even became the capital of all of Croatia by hosting the Royal Croat Council founded by empress Maria Theresa.
Not all was so bright in the history of this town, however: on April 25th, 1776, two thirds of the town buildings burned down in a large fire started in the suburbs. The fire was gone, but so was the capital honor: the Council moved to Zagreb and never came back. But they didn't let that deter them: they rebuilt the city in four years, and continued building more and more graceful palaces. Of particular mention is the building of the Croatian National Theater built in 1873 and designed by Vienna's famous architect Herman Helmer.
Today, the city's many historic landmarks and diverse industries (most known is perhaps Varteks, the local textile giant) make it a very desirable place to live in. Worthy of mention is the annual baroque music festival, the so-called Barokne Večeri, which always attracts some of the finest classical music artists and fans from the country and abroad, and often even helps various worthy causes such as restaurations of local pipe organs.
Another site that would be a real pity to miss in this county would be the beautiful castle of Trakošćan. Dating back to the thirteenth century (first written mention in 1334), it has been meticulously maintained and is currently one of the best preserved historic buildings in the country. And has decent competition, too, such as the nearby Klenovnik castle with 90 rooms and exactly 365 windows, once the seat of Parliament and now a working hospital.
This county encompasses most of the Hrvatsko Zagorje historic region, and it is a candidate for being the most idyllic county of them all: the many villages and small towns spread out across the hillsides are perfect for agriculture (vineyards in particular) and summer houses. Although, the many hills and valleys cause a peculiar effect throughout Zagorje: 15% of the year, the fog significantly lowers visibility in the area.
Perhaps the most astonishing landmark of the area is the excavation site of a 100000 year old Neanderthal man in caves near the central town of Krapina. A local archaeologist Dragutin Gorjanović-Kramberger found over eight hundred fossil remains back in 1899, suddenly catapulting the quiet little Hušnjak hill into worldwide fame.
The "modern" Krapina itself has been known since 1193, and always a favorite site for castles and other country houses of Croatian and Hungarian rulers. These days it's a reasonably developed little town, boasting its festival kajkavskih popevki sung in the local dialect of Croatian.
The town of Stubica features another thermal spring, the Stubičke toplice (yes, you guessed it, "toplice" means spa). Also in the area are medieval castles Veliki Tabor, Miljana, Bežanec, Hellenbach, Januševac...
This hyphenated county name obviously comes from two entities, the two of its largest cities, Koprivnica and Križevci.
Koprivnica is the official capital of the county, and has a history similar to nearby Varaždin: it was first mentioned in 1272 in a document by prince Ladislav IV and declared a free royal town by king Ludovic I in 1356, and flourished as a trading place and a military fortress since. The military aspect set it back some when it was included in the Military Frontier in the 16th century during the wars with the Ottoman Turks, but after Maria Theresa's decree of 1765 it resumed life as a peaceful little merchant town that really is.
Koprivnica developed significantly in the 20th century with the advent of the Podravka food industry, known worldwide for its Vegeta spice. They even have an alimentary museum of Podravka (whatever the hell that is :)). Worth mentioning is the annual "motifs of Podravina" event when the whole town becomes a gallery of naive art -- many of the Croatian greatest naive artists come from the villages along the Drava in this county.
Križevci, on the other hand, as a smaller city and second mentioned in the county name may seem like an underdog to it's neighbour Koprivnica. Its first mention was from 1193 by Bela III but it since the town was divided in two parts it didn't develop as fast: the so-called Lower Križevac only became a free royal town in 1405, thanks to king Sigismund. Križevac was the birthplace of a Catholic priest Marko who died at the hand of Calvinists in Košice in 1619, and was subsequently canonized because of his martyrdom.
After centuries of division, empress Maria Theresa united the Lower and Upper Križevac into Križevci in 1752. The town was also hit by the wars with the Turks, but it regained importance in 1871 when the railway was built through it on the way from Budapest to Rijeka.
These days the town is pretty much oriented towards mass entrepreneurship, but it still enjoys its eight beautiful cathedrals, built mostly in the Middle Ages.
The central town of Bjelovar is one of the younger towns, as it was first mentioned in 1413, and it only gained importance when a new fort was built in 1756 to defend against the Ottoman invasions. The town had to wait until the end of the wars to be pronounced a free royal town by ban Ivan Mažuranić in 1874.
The other part of the county name is for the picturesque hill of Bilogora that stretches along the northern edge of the county.
Named rather unimaginatively after the city of Zagreb that it surrounds, this county is all but unimaginative: it's center, the city of Samobor has been there since 1242 (according to a document of endowment by king Bela IV), and is one of the first tourist resorts in the region, with first tourist facilities dating back to 1810 oriented towards anglers, hunters and hikers.
Today the county's marching forward by piggybacking on the development of the nation's capital which it surrounds. Several towns, once mere villages,
such as Zaprešić, Velika Gorica or Sesvete, are latching onto Zagreb's conveniently nearby industrial zones and becoming larger than some of the centers of other counties. And then there's the outer rim which sports recreational facilities for the many residents of Zagreb (and anyone else who's willing to pay :)).
The central town of Karlovac is another fort from the times of the Military Frontier. It was built in the 16th century in an interesting location: where four rivers merge (Korana, Kupa, Mrežnica and Dobra), and in an interesting shape: as a six-side star fort. Its name is Carlstadt in German, after the archduke Charles of Habsburg. King Joseph II made it a free town in 1781 and the citizens could finally utilize the potential of being at the crossroads of paths from Pannonian plains to the Adriatic coast.
The town blossomed in the 18th and the 19th century with the development of roads to the seaside and waterways along the Kupa river. The 20th century wasn't so favourably inclined, what with all the wars and migrations, but the city's steadily recovering, once again being on the crucial geostrategic point in Croatia, where the continental regions touch the Mediterranean ones.
The county itself extends towards the north to the water springs of Jamnica (the logos of which everyone must have seen on Janica Kostelić's winter caps :), and towards the south all the way down to the mountainous regions of Gorski Kotar and Lika, in particular to the Bjelolasica mountain which features the largest winter sport recreation center in the country.
Named after the city of Sisak and the region Moslavina just across the river Sava, this county features the ancient Roman city of Siscia -- today's Sisak. Siscia was the largest city of the whole region back then, a Pannonian capital, probably due to its position on the joint of Kupa and Sava rivers. The city's patron saint is its first Christian bishop, St. Kvirin, who was tortured and almost killed during Diocletian's persecution of Christians: the story tells that they tied him to a millstone and threw him into a river, but he freed himself from the weight, escaped and continued to preach his faith.
The town may have lost importance with the fall of one empire, but it recovered it soon enough with the rise of another -- Sisak became famous for the crucial battles between the European armies and the Ottoman Turks. In particular, the battle of 1593 when the Turkish army first ever suffered a large defeat. The ban Toma Bakač Erdedi who led the defense in this battle became famous throughout Europe.
Nowadays, Sisak features the largest Croatian metallurgic factory (supported by the Faculty of Metallurgy also in the city) and the largest oil refinery. These are coupled with the petrochemical facilities in the nearby town of Kutina. Kutina is another nice little town, first mentioned back in 1256 by king Bela IV. Moslavina is probably the nicest part of this county, with the natural park Lonjsko polje near the rivers Lonja, Ilova and Pakra.
This county also extends far to the south to the border with Bosnia, and in this southern part of the county one can find a small town of Topusko, which has another one of those spas, although this one stands out with seniority: it dates back to the neolithic age.
For reference, local name of each of them is "$name županija", so e.g. Zagrebačka's full name is "Zagrebačka županija". (The suffixes -čka, -ska indicate genitive.) Note also that not all web pages referenced above have English versions, but just clicking around most of them should give you the right idea.