Vyšehrad used to be a seat of the first Czech king, Vratislav the Second. He left Prague Castle in favor of Vyšehrad, and created from it a place of high importance. Local church of Peter and Paul was subordinated directly to the Pope. During Hussite wars Vyšehrad was destroyed and what left is ruins of the old castle.
Church was however saved and in the 17 century Vyšehrad was changed in a massive fortification that still stands today, including three original gates.
There is also the oldest rotund (a chapel) in Prague standing there, and graveyard for the greatest Czechs of 19th century and early 20th century.
Many people believe that Vyšehrad contains strong spiritual power.