Exhibition game:

However, from 1971 to 1975, NBA teams played preseason exhibitions against American Basketball Association teams. In the early days of the NBA, league clubs sometimes challenged the legendary barnstorming Harlem Globetrotters, with mixed success. The NBA has played preseason games in Europe and Asia. In the 2006 and 2007 seasons, the NBA and the primary European club competition, the Euroleague, conducted a preseason tournament featuring two NBA teams and the finalists from that year's Euroleague.[citation needed] In the 1998-99 and 2011-12 seasons, teams were limited to only two preseason games due to lockouts.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What is the main European basketball club?
the Euroleague