After the First World War a first version of Yugoslawia was formed consisting of Croatia, Serbia and Slovenia. As a consequence the importance of Ljubljana grew as it became a regional capital. To reflect the growing importance and to create a distinct national identity in their capital they asked Jože Plečnik to remodel the city.
Jože Plečnik was a successful architect, having made himself a name in Vienna and Prague. In Vienna he was a figure of the Vienna Secession movement . In Prague he redesigned the Prague Castle.
He applied his ideas to the center of Ljubljana. The most notable structure to me were the river banks he constructed.
If you have ever been in Ljubljana you will have seen his work.
OUV
I am not sure that the narrative of the great Jože Plečnik holds. Looking at his wikipedia page I can't shake the feeling that an enthusiastic Slovenian optimized his English page. The German page is far less enthusiastic. Looking only at his CV he seems to be primarily of regional importance.
The buildings I saw in Ljubljana are not ground breaking. Indeed they seem to be watered down Art Deco buildings, nice to look at but inconsequential and a bit late to the party.
The two most distinctive examples of his style are the Roman city gate with the pyramid on top and the Trnovo Bridge. They are not special or great or even unique. Comparisons to Antonin Gaudi are way off target. And it does feel the Slovenians are trying to leverage the world heritage process to bolster the credentials of a national architect into a global star.
And to justify a bit why I say dated, I would point you to Kaunas, a city also redesigned after World War 1. The styles of the two cities could not be more different with Kaunas being ahead of the curve and Ljubljana behind.
Still, I do think Ljubljana overall deserves its place on the list. There is much here to like and I understand all the tourists flocking to the city.
Getting There
Ljubljana being the capital is well connected to all parts of Slovenia. There are direct busses to Idrija and busses and trains to the Skocjan Caves (Divaca). Google maps seemed complete with regards to the connections, schedules and bus stops.
To get out of Slovenia you will find plenty of bus connections. I came from Triest. There are also connections to Zagreb.