Zagreb Zoo, Croatia, this year (2020) became only zoo in the world with olm on display.
Despite that olm can also be seen in two cave vivariums: Postojnska Cave, Slovenia and Hermann's Cave, Germany (source: zootierliste.de).
Hi, both exhibits are in the same pavilion. On zoo map search for "Izložba zmije Hrvatske" (Snakes of Croatia exhibition). Snow vole is on ground floor, Olm is on first floor.
Each species is only in one exhibit. Balkan Snow vole has good condition for photos. But on my visit I go there 3 times to finally have luck that he was visible.
Olm, of course, usually don't move, it is very dark exhibit, as you can see on my photos.
Zagreb is a great zoo, have fun.
