It was named in honour of a visit of the Russian Tsar Alexander I to Berlin in 1805 but managed to escape renaming by the German Democratic Republic. During their rule the Fernsehturm TV-tower was built, giving visitors a magnificent overview over all of Berlin. The Nicolai church, survived the bombardment of World War II and is one of the oldest Berlin churches. Next to it is a large beautiful Neptun fountain, one of many fountains, heavily used by "dippers" during hot sweltering summer days.
The square is also famous for the GDR-era World Time Clock, a contintually rotating installation that shows the time throughout the globe.