LEGOLANDOn 7 June 1968, the first LEGOLAND Park was opened in Billund. This theme park featured elaborate models of miniature towns built entirely from Lego bricks. The three acre (12,000 m²) park attracted 625,000 visitors in its first year alone. During the next 20 years, the park grew to more than eight times its original size, and eventually averaged close to a million paying visitors per year. More than eighteen million Lego sets were sold in 1968.
In 1969, the duplo system went on sale. Duplo bricks are much larger than Lego bricks, making them safer for young children, but the two systems are compatible: Lego bricks can be fitted neatly onto Duplo bricks, enabling the transition to the Lego system to be easily made as children outgrow their Duplo bricks. The name Duplo comes from the Latin word duplus, which translates literally as double, meaning that a Duplo brick is exactly twice the dimension of a Lego building brick (2× height by 2× width by 2× depth = 8× the volume of a brick).