Sihlpost, Post office building near Zürich main station, Switzerland

Sihlpost is a six-storey reinforced-concrete office block of 123 m on Kasernenstrasse, opposite the Sihl and separated from the main station by Europaplatz. Its facade is a strict grid of windows with narrow piers, and the northern staircase is built as a tower, painted dark grey since 2016. The hipped roof is covered in slate, window-sill bands are of Mägenwiler Muschelkalk, and the only ornament is two stoneware mosaics by Carl Roesch at the entrances.

The SBB and PTT planned a new main post office from 1923; construction under architects Adolf and Heinrich Bräm began in September 1927, with engineer Robert Maillart responsible for the reinforced-concrete work. The shell was finished in late 1928, the SBB district directorate moved into the third to fifth floors in autumn 1929, and the post began operating in mid-1930. The sorting rooms were built with mushroom slabs and no ceiling beams so the machinery could fit.

The only ornament on the facade is a pair of stoneware mosaics by Carl Roesch flanking the two entrances. Inside, the sorting halls were built without ceiling beams so the mail machines had room, and the floors up to the second storey are mushroom slabs. Since 2015 the ground floor has held a Post branch, two restaurants and a shop.

The Sihlpost stands on Kasernenstrasse at the corner of Lagerstrasse, separated from the main station by Europaplatz. The Post office branch is on the ground floor, alongside two restaurants and a shop; the upper floors hold the KV Zürich Business School and Google offices and are not open to visitors. The north staircase tower has been painted dark grey since 2016.

Between 1938 and 1980 a 340-metre underground railway with a 600 mm gauge linked the Sihlpost to the post office at Zurich main station. Its driverless car carried up to 250 kg and ended in a lift that raised it to the ground floor. The line closed on 11 October 1980.