Vrindavan, Dwarka, and Jagannath are all extremely popular Hindu pilgrimage sites, attracting thousands of people each year, with Vaishnavas (Hindus devoted to the worship of Vishnu as the supreme being, especially his incarnation as Krishna) arguably making up the largest portion of the pilgrim populations.
All of these sites are located on or near bodies of water, with the Yamuna and Gomti rivers running through Vrindavan and Dwarka respectfully, and the Bay of Bengal beside the Jagannath temple. Rivers are often recognized as tirthas (spiritual crossings) and/or goddesses of their right. Hence, the geography only adds to the aura of sacredness around these sites. Being Hindu sites, the temples in these three places are tended to by Brahmin priests. These religious officials are responsible for conducting daily prayers (puja), officiating weddings, maintaining the temples in which they work, and adorning the murtis (image, statue, or idol of a deity) with appropriate attire.
In regards to the overlap in mythology, Vrindavan is believed to be the place where Krishna lived as an adolescent, while Dwarka is thought to be where he chose to live later in life, having asked the ocean to withdraw from the shore so that he could establish a city to call his own.
Vrindavan, Dwarka, and Jagannath are open to any and all peoples who wish to visit and show their devotion to a deity, appreciate Hindu culture, and/or celebrate the life/story of Krishna, Vishnu, and the like. Hence, they reinforce the theme of unity in diversity and the understanding of India as an “imagined landscape”.