This one is the best known, and took place in Zakopane, starting on 20 February 1940 in the villa "Pan Tadeusz", located at the Droga do Białego street close to the Dolina Białego valley.
The German side was represented by Adolf Eichmann and an official by the name of Zimmermann, who later became chief of the Radom District of the General Government territory.
The Soviet delegation was headed by Grigoriy Litvinov with—among others—Rita Zimmerman, director of a Kolyma gold mine.

According to several sources, one of the results of this conference was the German Ausserordentliche Befriedungsaktion (see: German AB Action operation in Poland), elimination of Krakow intelligentsia Sonderaktion Krakau and the Soviet Katyn massacre In his 1991 book Stalin: Breaker of Nations, British historian Robert Conquest stated: "Terminal horror suffered by so many millions of innocent Jewish, Slavic, and other European peoples as a result of this meeting of evil minds is an indelible stain on the history and integrity of Western civilization, with all of its humanitarian pretensions".
Also, Professor George Watson of Cambridge University concluded in his "Rehearsal for the Holocaust?"
commentary (June 1981) that the fate of the interned Polish officers may have been decided at this conference.
This is however disputed by other historians, who point out that there is no documentary evidence confirming any cooperation on that issue, that the existing Soviet documentation actually makes such a cooperation improbable and that it is reasonable to say that Germany did not know about the Katyn massacre until the mass graves were analysed by the Katyn Commission.

The fourth and last meeting took place in March 1940 in Krakow.
According to some historians, it was part of the Zakopane Conference.
This event was described by General Tadeusz Bór-Komorowski, commander of Armia Krajowa in his book Armia Podziemna (The Secret Army).
In it, he describes how a special delegation of NKVD came to Krakow, which was going to discuss with Gestapo how to act against the Polish resistance.
The talks lasted for several weeks.

Russian historian Alexandr Nekrich describes formal military cooperation agreement signed on 20 September 1939 where both sides committed to "cleansing of hostile population" and "liquidation" of Polish resistance.

Historian Wojciech Materski points out that there is evidence of clandestine murder operations conducted by both Soviet and German forces in 1939–1940 across occupied Poland, however, there is no evidence of direct connection between the NKVD prisoner massacres and the German AB-Aktion in Poland leading to massacre of several thousand prominent Poles in the same time-frame.
This one is the best known, and took place in Zakopane, starting on 20 February 1940 in the villa "Pan Tadeusz", located at the Droga do Białego street close to the Dolina Białego valley. The German side was represented by Adolf Eichmann and an official by the name of Zimmermann, who later became chief of the Radom District of the General Government territory. The Soviet delegation was headed by Grigoriy Litvinov with—among others—Rita Zimmerman, director of a Kolyma gold mine.
According to several sources, one of the results of this conference was the German Ausserordentliche Befriedungsaktion (see: German AB Action operation in Poland), elimination of Krakow intelligentsia Sonderaktion Krakau and the Soviet Katyn massacre In his 1991 book Stalin: Breaker of Nations, British historian Robert Conquest stated: "Terminal horror suffered by so many millions of innocent Jewish, Slavic, and other European peoples as a result of this meeting of evil minds is an indelible stain on the history and integrity of Western civilization, with all of its humanitarian pretensions". Also, Professor George Watson of Cambridge University concluded in his "Rehearsal for the Holocaust?" commentary (June 1981) that the fate of the interned Polish officers may have been decided at this conference. This is however disputed by other historians, who point out that there is no documentary evidence confirming any cooperation on that issue, that the existing Soviet documentation actually makes such a cooperation improbable and that it is reasonable to say that Germany did not know about the Katyn massacre until the mass graves were analysed by the Katyn Commission.
The fourth and last meeting took place in March 1940 in Krakow. According to some historians, it was part of the Zakopane Conference. This event was described by General Tadeusz Bór-Komorowski, commander of Armia Krajowa in his book Armia Podziemna (The Secret Army). In it, he describes how a special delegation of NKVD came to Krakow, which was going to discuss with Gestapo how to act against the Polish resistance. The talks lasted for several weeks.
Russian historian Alexandr Nekrich describes formal military cooperation agreement signed on 20 September 1939 where both sides committed to "cleansing of hostile population" and "liquidation" of Polish resistance. 
Historian Wojciech Materski points out that there is evidence of clandestine murder operations conducted by both Soviet and German forces in 1939–1940 across occupied Poland, however, there is no evidence of direct connection between the NKVD prisoner massacres and the German AB-Aktion in Poland leading to massacre of several thousand prominent Poles in the same time-frame.
Gestapo–NKVD conferences