The oldest cityscape of the city of Zurich (attributed to Hans Leu the Elder) consists of five panels. It originally represented the martyrdom of the patrons of the city, but was mutilated after the Reformation. In 1981-82, the panels were examined with x-ray and infrared reflectography. This examination yielded information about their original dimensions -- even in their truncated state the panels have a total length of 536 cm. The backs of the panels were not painted. Thus they could not have belonged to the wings of an altarpiece. Bosshard, in collaboration with Daniel Gutscher, has hypothesized that the panels hung in the Chapel of the 12 Apostles in the Grossmünster. Repainted architectural elements and those newly applied in place of figures were used to date the changes made after the Reformation -- the terminus ante quem of 1576 is suggested as a supplement to the terminus post quem of 1566 fixed by Salomom Vögelin. See also 20-663. -- AATA