Definitely not for those with Acrophobia.
Glass Floor [Pics]
http://www.archibase.net/archinews/14539.html
A glass floor is transparent section of a floor in a building or a boat. Usually made of a reinforced glass, the most common use is as a tourist attraction. Glass bottom boats are popular for allowing a better view into the sea.
The highest above ground level is in the CN Tower in Toronto ( 1815 feet) that can withstand a pressure of 4,100 kilopascals (600 lb/in²). The highest glass floor in a building in Europe is in the Spinnaker Tower in Portsmouth (557 feet). The highest in Oceania is in the observation deck of Sky Tower in Auckland (1076 feet).
Glass as a flooring material is also in both residential and commercial structures. Special hollow glass blocks known as glass pavers are often used in combination with a steel or aluminum frame.