The Meguro Parasitological Museum is one of the strangest and most memorable museums in Tokyo. Founded in 1953 by Dr Satoru Kamegai, it is the only museum in the world dedicated entirely to parasitology, and its collection of over 300 preserved specimens — roundworms, liver flukes, tapeworms, bot flies — is genuinely fascinating and genuinely disturbing.
Despite its subject matter, the museum draws large crowds, particularly young couples (it was once voted one of the most popular first-date spots in Tokyo, apparently due to the bonding effect of shared disgust). The displays are bilingual and well curated, the admission is free, and the whole visit takes about an hour. Not recommended immediately before or after meals.