The temples of My Son lie an hour and half by car west of Hoi An. They are historically very significant as they were the religious and political capital of the Cham Kingdom. Although dwarfed if compared to Angkor Wat, they are definitely worth a visit, the on-site museum gives some context and explanation of Hindu symbolism. Arrive early to avoid crowds, exploring the lush grounds by yourself as the sun rises is a nice and peaceful experience.