Not just phallic symbols of power; they actually served a practical purpose.
These concrete towers were unique AIR RAID SHELTERS of Nazi Germany, built to withstand the destructive power of WWII bombs and heavy artillery. Their cone shape caused bombs to slide down the walls and detonate only at a heavily fortified base.
Cheaper to build above ground than to dig bunkers, they were quite effective, as it was possible to cram as many as 500 people inside. Plus the "footprint" of such tower was very small when observed from the air, so it was very hard for the bombers to ensure a direct hit.
(photo credit: Ivo Schenk. This tower you can even visit)
First appearing in 1936, they were quickly dubbed "cigarette stubbs" or "sugar beet heads". Officially they were called Winkeltürme (Winkel Towers)- after their architect Leo Winkel of Duisburg. Winkel patented his design in 1934, and in the following years Germany built 98 Winkeltürme of five different types.
Hitler was quite impressed by Winkel's concept and blueprints, and ordered full engineering and production support. They were meant to be shelters for factory workers and railroad personnel, to be placed mostly in heavily industrial areas, such as Giessen. Here is a cut-away view:
"The Winkelturm in Stuttgart, a Type 2, is in the Feuerbach rail area. The cone shape was designed to defeat bombing attacks by deflecting bombs off the top and sides, toward a reinforced area around the base. However, a Winkelturm of this type in Bremen suffered a direct hit by U.S. bomb in October 1944, which exploded through the roof and killed five people inside."