If you arrive to Prague Old Town Square through Kaprova Street or Parizska Street, you will go past a large Baroque church at the corner of the square. It is the St. Nicolas Church, built by one of the masters of Baroque architecture K. I. Dienzenhofer. Especially the interior of the church is impressive.
St. Nicolas Church - Old Town on map of Prague:
Other Prague attractions near St. Nicolas Church - Old Town