The fastest vessels on the Gulf of Finland cover the 80 kilometres between Helsinki and Tallinn in about two hours, which places the Estonian capital closer to central Helsinki than several Finnish commuter towns are by rail. That accident of geography has produced one of Europe's busiest short-sea corridors, moving millions of passengers a year between West Harbour and the Tallinn terminals. The Helsinki Tallinn Guided Day Tour with Ferry Crossing is only the modern expression of a route Hanseatic merchants worked under sail six centuries earlier, when salt, herring and Novgorod furs passed the same headlands. Tallinn's Old Town was entered on the UNESCO World Heritage list in 1997 and survives as one of the most complete medieval urban cores in northern Europe. Roughly 1.9 kilometres of defensive wall still stand, punctuated by some twenty towers, among them the squat artillery bastion called Fat Margaret and the fifteenth-century gun tower Kiek in de Kök, whose name means peep into the kitchen. The lanes themselves cost nothing to enter: access to the Old Town streets and public squares is 0 EUR, a rare condition among Europe's walled cities. Vanaturg 2 marks the old market corner, a few paces from ground that has carried civic trade since the thirteenth century. The city divides vertically. Toompea, a limestone outcrop, lifts the seat of parliament, a Baroque-fronted castle and the onion domes of Alexander Nevsky Cathedral, consecrated in 1900, above the merchant town below. Down in the lower quarter the gables remain Gothic and the doorways carved. The Town Hall, completed in 1404, is the only surviving Gothic town hall in northern Europe; its weathervane, Old Thomas, has turned above Raekoja plats since 1530. St Olaf's Church, measured at 159 metres in the sixteenth century, was plausibly the tallest structure on earth and has been struck by lightning at least eight times. A Helsinki Tallinn Guided Day Tour with Ferry Crossing tour concentrates its walking hours on this compact ridge and the streets beneath it. Such density explains why a Tallinn Old Town guided tour from Helsinki works as a single day rather than an overnight. The walkable core measures barely a kilometre across. Helsinki Tallinn Guided Day Tour with Ferry Crossing tours pair the sailing with a guided circuit of Vanalinn; the ferry-only options serve travellers who intend to navigate the limestone lanes unaccompanied. Either way the sea leg frames the city, and Tallinn is approached as it was always meant to be approached — from the water, spires first.