The Barbican Estate is a residential estate that was built during the 1960s and the 1980s. An icon of Brutalist Architecture the Barbican Estate is an unique and complex real life experiment; a city within a city. The main focal point of the estate is the lake and its neighbouring terrace. High above and behind the terrace is the Barbican Centre, the largest performing arts centre in Europe. I really rate their visual culture exhibitions (for instance, Jean-Michel Basquiat and the Bauhaus) and live concerts (Nils Frahm and Ryoji Ikeda). Love it!
Just above the Dorfman Theatre lobby at the National Theatre, is the entrance to the high-level walkway, a public walkway that overlooks the National Theatre props and scenic workshop.
It's free and is a unique chance to get a glimpse of what happens backstage. I love popping in when I'm on the south bank, as you get a completely different sight each time, depending on which production the workshops are working on at the time.