Petr Pavlensky has been taken into custody by police for his latest piece protesting state surveillance

Culture bus heads to Washington in bid to change attitudes to the Middle East

New framework stresses return principle but some fear that traffickers in illicit objects could abuse it

Greta Moll’s heirs argue painting was “misappropriated” in 1947

Antonello da Messina’s triptych brought together in 15-year loan agreement

Boris Johnson says Smithsonian Institution still on board as capital’s planned cultural quarter on former Olympics site gets £45m in donations

Austrian collector previously supported Frieze Projects with her prize

Participants, including Douglas Coupland, invest in a simulated stock market shaped by technological developments

Proposal is one of three being considered by Southwark Council in south London next week

Artists’ foundation takes over former factory that served as Otto Piene’s fire studio—and party centre

Renovation of the Pergamon Museum expected to be complete by 2019, with a new wing dedicated to Egyptian art to open by 2026

Artist links delayed arrival of Event Horizon with pro-democracy movement and taboo subject of suicide

Yayoi Kusama and Random International are latest victims of China’s copycats

Full-scale re-creation is part of ambitious new display of masterpieces at Museo dell’Opera del Duomo

Hirshhorn holds preliminary talks but Berlin first in queue to borrow works by artists such as Gauguin, Pollock, Rothko, Picasso and Bacon

Arts professionals are generally optimistic about the country’s new leadership—although some worry promised changes could be too little too late

While government moves to limit right to strike by reclassifying museums as “essential public services” on a par with schools and hospitals

The vast installation at the Grand Palais reflects the changing world order

Jean-Antoine Houdon's sculpture of the goddess Diana was taken by the Nazis during the Second World War

Our pick of the inaugural biennial, which opened to towering expectations

Institutions are burgeoning in the face of sanctions and currency devaluation

Interest grows in younger generation active in Tehran’s lively art scene and the Iranian diaspora

Natural history museum is more receptive than city’s art spaces