SCL's Aleksandar Belic, Antun Balaz and Dusan Vudragovic visited Barcelona Supercomputing Center (BSC) and its supercomputer installation Mare Nostrum on 25 September 2009. MareNostrum is one of the most powerful supercomputers in Europe, currently at the position 60 at the Top 500 list. In the discussion with Mare Nostrum operations group, they exchanged the knowledge on applications, organizational aspects, system administration, security, resource management, networking, and user support.