The walls around Tallinn Old Town are still almost complete - which is very rare in Europe. You can walk along the top of sections of the wall and look out over the city's orange rooftops and down to the Baltic Sea. Some of the towers have their original wooden staircases inside.
The Old Town sits on two hills. The upper hill, called Toompea, is where the most important buildings were placed, including a tall church called Alexander Nevsky Cathedral whose onion-shaped domes you can spot from far away. The lower town below it was where merchants and craftspeople lived and worked.
In the middle of the lower town is the Town Hall Square, which has been a market place for about 800 years. In summer it fills with café tables; in winter it becomes one of Europe's most famous Christmas markets, with glowing lights and the smell of warm spiced drinks drifting through the cold air.
Tallinn Old Town is a UNESCO World Heritage Site, which means it is recognised as a treasure belonging to all of humanity. Almost the entire street plan from the medieval period still survives - the roads twist and turn in the same places they did 700 years ago.