Driving on the B2 ("Bundesstrasse") between Potsdam and Berlin, at the roundabout in the suburb Groß-Glienicke turn off onto the Sacrower Allee. Follow the road and stay straight ahead on the Sacrower Allee (even when the main road turns left, changing into Richard-Wagner Street) and follow the small road all the way to the start of the forest; follow that forest road which is called "Im Königswald"  (signage to the Institute is present) until you reach the entrance gate to the Institute's grounds. You'll find signage to the parking lots.

Attention: The described route via Sacrower Allee in Groß-Glienicke is the only working route. Sometimes, navigation systems show alternative routes, however, they are incorrect. Do not follow those instructions, as you will end up on dead-end forest tracks in the national park, and will be forced to turn back.

-from Berlin/Spandau main train station: 

Take Bus No 638 towards Potsdam, Campus Jungfernsee and alight at the bus stop Sacrower Allee/Richard-Wagner-Strasse; from there you will have to walk along the Sacrower Allee and the  forest road "Im Königswald" for about 1.8 km, which will take about 20 min; signage to the Institute is present on the forest road

-from Potsdam main train station:

Take the inner city train "Tram" No 96 towards Potsdam Campus Jungfernsee to the end station; there board the bus No 638 towards Berlin/ Spandau, alight at the bus stop Sacrower Allee/Richard-Wagner-Strasse and walk as described above