Surrounded by gray walls made of concrete for many years. In the Swiss town of Lenzburg, however, the situation is somewhat different: from fall 2012 to spring 2014, well-known Swiss street artists designed 4661 square meters of wall space at the new local penitentiary. They were free to draw or spray paint anything they wanted. In more than 25,000 hours of work, a total of 1,400 spray cans and 200 liters of paint were used to turn a barren, cold concrete bunker into a lively and unique comprehensive work of art. This impressive and tangent art across eight recreation courtyards, five colonnades, a staircase, and two oversized exterior walls remains, similar to the prisoners themselves, locked up behind the heavily guarded gates and walls. The wall paintings and graffiti are made available to the public in this art book. In addition to a presentation of the works of art, 4661 m2 also provides an insight into the work processes while also allowing the 16 involved artists to speak about their efforts.