Science buffs in Barcelona must make the CosmoCaixa a stop on their way around town. This science museum was built in 2 parts – one completed in 1909, and the other section essentially a century later, in 2004. This museum is especially valuable for instilling scientific curiosity in your young ones. With exhibits like the planetarium, which take you through space in a visual extravaganza, and the flooded forest, which imitates the Amazon Rainforest with as much accuracy as possible, your little tykes are bound to be filled with awe (and questions).