Tallinn City Wall is the defensive wall constructed around the city of Tallinn in Estonia. The first wall around Tallinn was ordered to be constructed by Margaret Sambiria in 1265 and for that reason, it was known as the Margaret Wall. This wall was less than 5 m high and about 1.5 m thick at its base. Since that time it has been enlarged and strengthened. The walls and the many gates are still largely extant today. This is one of the reasons that Tallinn's old town became a World Heritage Site. The walls were enlarged in the fourteenth century, and citizens of Tallinn were required to turn out for guard duty, which meant to wear their armour and demonstrate their readiness to face off invaders.

A good opportunity to get a glimpse of the town's Medieval defenses can be found at the Hellemann Tower, which stands adjacent Müürivahe street next to Old Town's knit market. The 3-storey tower dates back to the 14th century and at different times was used as a prison and a weapons store.

Nowadays it serves a more peaceful purpose: housing an art gallery. Visitors not only get to see the tower, but they can also walk along a 200-metre stretch of the town wall, from where they'll get fantastic views of the Medieval city.