The Sevii Islands are a series of Islands located south of Kanto. These islands can be accessed by going to the Vermilion City docks.
Despite the name Sevii Islands, there are nine islands (Seven initially accessible, two accessible by promotion).
The name "Sevii" is a corruption of the English word for Seven, containing the Roman Numeral "VII" as a suffix. It was named the Sevii islands because it was believed to have been created in seven days.
Tri Pass allows the player to visit islands 1, 2 and 3.
Rainbow Pass allows the player to visit islands 1, 2, 3, 4, 5, 6 and 7.
Special Tickets (obtainable through promotions) allow the player to visit the remaining two islands as defined by the ticket.