A railway through and under the archipelago, a "Sea Railway", not a railway at the coast line but over and under the sea itself. Not a railway under the sea as the Dover - Calais but also over the sea on bridges.
As can be seen on the map the solution is based on a huge amount of bridges and tunnels. The exact amount of bridges and tunnels cannot be determined before a detail planning is done for the suggested railway. There is of course the possibility to dig deeper under the sea floor and reduce the amount of tunnels and bridges in this way. Tunneling under the sea floor is risky and we have here chosen a more cautious solution. In general it is supposed that under the sea floor you will find rock, Finnish granite, but even if we find this rock it is still full of dangerous cracks. No real study has been made, of this magnitude of the sea floor, to check how deep under the floor you really find rock.
A sea depth graph starting from Kapellskär to Karis. (Note that X-axis is in kilometers and that Y-axis is in meters)
The graph above will give the reader some understanding about the sea depth. We are talking about rather shallow waters with a maximum depth of 63 meters. It also important to beware of that this part of the Baltic Sea will froze at winter, almost every year. In many cases can you walk from island to island over the ice, and some years can you drive your car from Åland islands to the Finnish mainland by ice road. Sea of Åland is also some years covered by ice during some part of the winter but driving a car over the ice to Sweden has not been possible, but maybe we will, someday, have such a winter.