Vyšehrad is a nice attraction a bit outside the inner city of Prague. It can though easily be reached taking the metro to the stop Vyšehrad. It is assumed that this fortress/castle was built in the 10th century, and the legend has it that the first Slavic tribes started constructing here.
Today you can see the Basilica of Saint Peter and Paul in Vyšehrad, and the visitors can also enjoy the oldest rotunda in Prague, the Rotunda of Saint Martin. Besides this there is a cemetary in the area and a great view towards the river Vltava.