As the coastal Montenegro and Kotor become more popular destinations, thanks partly to Kotor's status as a double WHS, I thought I would add my memorable experience there from back in April, 2010. 

From the castle I made a detour to the only house on the slope of the mountain (to get the free water springing out at the entrance) and headed up from there on the zigzag Old Kotor Trail all the way to the point called "Top of the Old Kotor Trail."  The altitude of the castle is 200 m, but that of the Top is 500 m, so you can perhaps imagine the even more dramatic view over the Kotor Bay from the Top.  

The hike from the castle to the Top took probably about 2 hours and another 1.5 hours to come back down to the town of Kotor. To be sure, all of this is within the core zone of the WHS. 

When I mentioned my plan to hike up to the Top at the tourist kiosk in Kotor, they did not recommend it, as the trail is not designed for tourists and was not in the good shape at least at that time in 2010.  But the fact was that the Old Kotor Trail between Kotor and Cetinje located on the other side of Lovcen National Park has been used over a millenium to transport goods on the back of donkeys!  In fact I saw a local with two donkeys on the trail even in the 21st century, although I don't think he was going all the way to Cetinje.  I would highly recommend this historic trail. This was one of the best half-a-day hikes I've ever done.  

But in fact the best part for this hike was not the trail itself, the view or even the donkeys, but a goat.  This goat I encountered on the way back near the Top followed me, to my disbelief, for several kilometers all the way down to the house where, as it turned out, she belonged. (All of this is photogenically chronicled at the link below.)  It was no surprise, then, that the family of the house had given me a freshly-made round goat cheese with the diameter of about 20 cm on my way up and now even runs a Cheese Shop at the house, according to Google Map. 

Alternatively, if you have a car, you can drive to the top of Mt. Lovcen at 1750 m in the namesake National Park, where you can supposedly see not just the Bay of Kotor, but also all the way to the Adriatic Sea. But this NP is not part of the WHS. 

One more thing about this area.  Although I did not get to Perast, seeing Els' photo of the squid mosaic from the Roman times is VERY interesting to me (although I may not have recognized the motif as a squid myself) because it was right here in Kotor in 2010 when I had what I thought was the best seafood dish I've ever had, which was grilled small squids in olive oil with garlic.  Maybe this dish has been around here since the Roman times...