Two to three hours by train from Tokyo station, the Izu Peninsula offers numerous hot springs and seaside resort towns, so it is a popular day trip and weekend get-away destination for many Tokyoites.
Atami and Shimoda are perhaps best known, but there are dozens of less renowned towns on both sides of the peninsula, and in the interior, with inviting attractions.
Odawara and Atami are serviced by the Tokaido Shinkansen. From Atami to Ito, the Ito Line, and other towns on the east side of Izu are serviced by the Izukyu Railway between Ito and Shimoda. The interior of Izu has the far less convenient Sunzu line from Mishima and west coast has no train service. Tokyo to the southern tip of Izu can cost up to ¥5500.
The east coast has good highway service from Odawara to Shimoda. The interior has several roads, including the Izu Skyline Road (toll) from Hakone to approximately the middle of Izu. This popular road runs along the mountain crest and has very nice views on clear days. Roads on the west side are narrower and have enough turns to slow progress significantly. Although the driving speed is average for Japan (60km/h) don't plan on making more than 20km/h straight-line progress. The section between Atami and Odawara is usually gridlocked on Sunday evenings, particularly in the summer. Turning inland at Atami and going through Hakone is often a faster return to Tokyo despite the extra distance.
Izu Peninsula is recognized in the scuba diving community as the most popular destination for mainland Japan diving. The East Coast of Atami is most popular with dive operators for its accessibility and infrastructure, while the West Coast's sites are largely unspoiled, safeguarded from weekend crowds by its remote destination and lack of train stations.