This 20 meter tall monument was erected in 1715 as a thanksgiving to the end of a plague. It is also called a plague column or Marian column.
Designed by Giovanni Batista Alliprandi

On the left is the Liechtenstein Palace (Malostranské náměstí). It was built in 1621 by connecting 5 existing houses for Charles Liechtenstein, who amassed his fortune by confiscating protestants properties at the start of the Thirty Years War. It now houses a music conservatory.
Above it is St. Vitus Cathedral in Prague Castle.