Tallinn's public transport is free — but only for residents. Visitors need a valid ticket, and the fine for not having one is €40. The good news: fares are cheap and the network is straightforward. For most of your stay in Old Town, you probably won't need it much at all. The Old Town: Walk First Most of Tallinn's main attractions sit within a compact medieval core you can cross on foot in around 30 minutes. From Viru Gate to Toompea Hill, from St. Olaf's Church to Town Hall Square — everything is walkable, and walking is genuinely the best way to see it. Cars are restricted in large parts of…