Tallinn's atmospheric Old Town is an enthralling hodgepodge of medieval streets and spires. It's a small city, and the tourist areas are safe and easily explored on foot. Buy a Tallinn Card if intending to use buses, trolleys or trams. For a look into Tallinn's past, visit Rocca-al-Mare Open Air Museum's typical rural Estonian taverns, windmills and watermills, see the onion-domed 1900 cathedral or join the bustle in historic Town Hall Square. St. Olav's spire was once the tallest in the world.