"Walking along the winding streets of central Copenhagen , you will invariable chance upon the 17th-century Round Tower, with an observation deck that affords great views over the city and to Sweden in the distance. To reach the top, you walk up an interior spiral ramp with no stairs, designed to allow horses and carts in earlier times to ascend to the library and observatory, and today kids have great fun racing up and down the cobbles. The tower is also the site of an annual unicycle race. The record round-trip time so far: just under one minute 50 seconds."