He designed several major buildings around the world, including the Opera House in Kyoto and the Museum of Contemporary Art and Design in Den Bosch in the Netherlands. He is the author of boutique interiors of the fashion designer Karl Lagerfeld.
Following the collapse of communism in Czechoslovakia, Sipek returned home in 1990 to become the architect of the Prague Castle during the presidency of Vaclav Havel. He designed some furniture and glass artifacts in the interior of the Castle as well as the Castle Gallery and the entrance to the Presidential Office. He also created official glass gifts for foreign visitors.
Most recently, Sipek became the designer of the symbolic “Havel’s Places” or benches that have been dedicated in many places around the world.
A large retrospective exhibition of Sipek’s works, entitled “Out of Limits,” was opened in the Dancing House in Prague on Havel’s birthday last October.