Stock-im-Eisen

The Stock im Eisen is the midsection of a tree-trunk from the Middle Ages, a so-called nail-tree, into which hundreds of nails have been pounded for good luck over centuries. It is located in Vienna, Austria, in Stock-im-Eisen-Platz, now part of Stephansplatz, at the corner of the Graben and Kärntner Straße and is now behind glass on a corner of the Palais Equitable.

Source: Wikipedia