Prague. Cathedral of Saints Vitus
The Metropolitan Cathedral of Saints Vitus, Wenceslaus and Adalbert (or just Saint Vitus Cathedral) is the most visited landmark of the whole Czech Republic, which is, in spite this fact, known as the most atheistic European country.
The construction of the present Gothic-style Church began in 1344, but it was finally finished only in 1929. So it took nearly 600 years to complete it.
The Cathedral has regular religious services. Some believing people even say that it is the most sacred place in the country, since the remains of the major patrons (Vitus, Wenceslas, Adalbert, Sigismund and John of Nepomuk) are all kept here.