The 17th Century was not the best time for Slovakia, or for the rest of Central Europe. Slovakia itself was fully incorporated into the Kingdom of Hungary, as it had been for centuries. It was simply known as "Upper Hungary" in those days as it was the northernmost part of the Kingdom. Slovakia was by no means the only non-Hungarian country to be the part of the Kingdom of Hungary: Croatia was there, so were parts of Rumania, and other territories.
But the Kingdom of Hungary was not an independent monarchy in the 17th Century. Though it had its own nobility, the Kingdom itself was fully incorporated into the Austrian Empire, not Austro-Hungarian Empire yet, just Austrian Empire. Of course, the Austrian Empire and the Austro-Hungarian Empire were the same as far as territory is concerned, but back when it was only Austrian Empire all power was fully concentrated in the hands of the Habsburg Emperor of Austria. Of course, the Hapsburgs were the Emperors until the 20th Century, but they gave a relative autonomy to the Kingdom of Hungary toward the end. But not so in the 17th Century.
But the Austrian Empire had enough troubles of its own in the 17th Century: It had to fight the Turks. The Turks were quite successful initially, and got control of most of the Kingdom of Hungary (except for Slovakia - they were never able to get through the mountains) and the rest of the Austrian Empire (except for most of Bohemia and Moravia).
Around the mid 17th Century a Hungarian prince named Rakoczi started a rebellion against the Emperor. He organized a rebel army that fought the imperial forces for the rest of the 17th Century and for the first decade of the 18 Century. After Rakoczi's death the 21-year-old Imrich Tokoli became the leader of the rebellion.
The rebellion started in Eastern Slovakia but lasted long enough to spread all over Slovakia, parts of Moravia and even as far south as Croatia.
The people of Slovakia called the rebels kuruci (plural of kuruc) which is how Slovaks pronounced the Turkish word for rebel. In other languages, it is often spelled Kurutz or Kurucz. In all of them the "c", "tz", or "cz" are pronounced like "ts" in English. All three forms also survived as family names.
During the long period of the rebellion the kuruci occupied most of the cities of Slovakia (and surrounding areas mentioned above). They also occupied most of the many castles found in Slovakia. They had a very nasty habit of burning each city and each castle down whenever they left it. The castles that were not burned to ground by the kuruci were burned down by the imperial forces.
So, sadly, most of ancient Slovak castles are ruins these days, compliments of the kuruci. That includes the legendary Castle of Sitno which was built in the late Bronze Age.
The kuruci were completely defeated in 1710 or 1711.