Located South-West of Tokyo and right South of Mount Fuji, the Izu Peninsula faces the Pacific ocean and is part of the Fuji-Hakone-Izu National Park.
Noted for its beautiful coastal scenery and hotspring resorts, it is popular with Tokyoites on weekends and national holidays. In fact, it is officially Japan's most tourist area, but this is explained more by its proximity to the Tokyo metropolis than its actual touristic value.
Short-term tourist shouldn't bother too much about Izu, except if they want to experience Japanese thermal springs ("onsen"). The main onsen resort towns are Atami, Shuzenji, Shimoda and Ito.
Probably the most pleasant town to stay in the peninsula, Shimoda is also the most interesting historically.
This is where Commodore Perry and his Black Ships first came to Japan to negotiate the country opening of its port to US ships. In 1854, the the Shogunate and the US signed a Treaty of peace and amity, which effectively ended Japan's 250 years of self-imposed isolation.
Consequently, Shimoda was, along with Hakodate, the first port open to Western ships. The first American consul, Harris Townsend, established his consulate in Shimoda in 1856.
How to get there
The shinkansen links Tokyo to Atami in about 50min (around ¥3,600). Regular trains make the trip in about 1h40min and cost ¥1,890.
Several train lines (Shinkansen, JR Superview, JR Ito, Izu Kyuko...) link Izu's towns. As times and fares depend on the line and connections, you had better check Yahoo Transit or Ekitan from our Transportation in Japan page for exact fares and timetables.