The Coca Museum (Museo de la Coca) is on Calle Linares in the market district, squeezed into a narrow building that opens up more than you expect. The displays cover the deep history of coca use in Andean cultures — ritual, medicinal, social — and the botany of the plant itself, and then move into the modern political history: how the United States pressured Andean governments to eradicate coca cultivation as part of the war on drugs, how Bolivia under Evo Morales (himself a former coca grower) pushed back, and the ongoing tension between a plant that has been central to Andean life for millennia and an international drug control framework that conflates it with cocaine. The museum is small but well-researched and takes a clear position, which makes it more interesting than a neutral presentation would be.
You will leave understanding why Bolivians are so genuinely bewildered and annoyed by the international status of coca. Chewing the leaf (acullico) is legal, widespread, and socially normal here — office workers, bus drivers, police officers all do it. Coca tea is served everywhere and is genuinely useful for acclimatising to the altitude. The museum makes the contextual case well. There is a small shop selling legal coca products at the entrance. Admission is cheap; the whole thing takes about 45 minutes.