It is said: tīrthī-kurvanti tīrthāni. A tīrtha, or holy place, is a place where great saintly personalities visit or reside. Although the holy places were already places of pilgrimage, they were all purified by Śrī Caitanya Mahāprabhu’s visit. Many people go to these holy places and leave their sinful activities there, thus becoming free from contamination. When these contaminations pile up, they are counteracted by the visit of great personalities like Śrī Caitanya Mahāprabhu and His strict followers. Many kinds of patients come to a hospital, which may be infected by many types of disease. Actually the hospital is always infected, but the expert physician keeps the hospital sterilized by his expert presence and management. Similarly, places of pilgrimage are always infected by the sins left by the sinners who go there, but when a personality like Śrī Caitanya Mahāprabhu visits such a place, all contaminations vanish.
Ref>>Srila Prabhupada Vani.