Tallinn Zoo spreads across a large site in the western part of the city, far from the medieval lanes but still easy enough to reach by public transport. Its strongest suit is space: this is a broad, outdoor zoo with a mix of northern-climate animals, mountain ungulates, big cats, birds, and family-friendly exhibits.
It is not a must for a short Old Town-focused visit, but it earns its place for families or anyone staying long enough to see modern Tallinn beyond the postcard centre. Dress for the weather, since much of the visit is outside and the Baltic wind can make even mild days feel brisk.