This building, known as a limonaia, is an active relic of the technology used to grow lemon trees along the western shore of Lake Garda. Apparently the Franciscans began this work several centuries back, and it continued into the 19th century, when a variety of factors (depending upon which source you read) brought it to a close, leaving these prominent and distinctive structures to gradually deteriorate, or to be renovated and reused as houses (with lots of tall pillars in the gardens). An elaborate process of covering the front and sides of the structure with boards (and if necessary lighting fires inside) protected the citrus trees during cold spells in the winter. This industry supplied central Europe with citrus fruit for centuries. A more complete description is available at http://www.lagodigardamagazine.com/lago-di-garda-limonaie.aspx (this comes up in Italian, links to translate to German or English are at the upper left hand corner of the page.)
This is my letter to the world 