Kōtoku-in is a Buddhist temple in Kamakura, famous for the "Great Buddha" statue. The large bronze statue is of Amida Buddha, one of the most recognizable in Japan.
Admission to the temple is only 200 yen (as of Dec. 2013). You can also go inside the Great Buddha for an additional 20 yen (as of Dec. 2013).
Go in the fall when the leaves are changing colors, as the reds, oranges, and yellows are gorgeous. Or if you're lucky enough to time your trip right, go in the spring when the cherry blossoms are blooming.
Directions from the Kōtoku-in official website: From Kamakura: Get off at JR Yokosuka Line Kamakura Station. Change to the Enoshima Electric Railway (bound for Fujisawa) and get off at Hase Station, the third stop (approx. seven minutes from Kamakura). Kotoku-in is a seven-minute walk from the station.