The low countries of Belgium and the Netherlands, and the Maldives, are quite worried, and justifiably so, about the rising ocean. All three countries are very close to sea level, and parts of the Netherlands were actually reclaimed from the sea at great effort and expense. This post concerns the Netherlands and Belgium the most, as the Maldives can't afford this solution just yet.
I think, starting from the German border, we should carefully record each building's blueprint, demolish it, and rebuild it on poles 60 meters high. We'd also retrofit the plans for things useful to the people, like electricity, phones, central heating and air conditioning, and whatever else could sensibly be installed in the plans, because, well, why not. The streets would be on poles (like a freeway), the houses on poles, with yards on poles. It would be very tall. We'd sweep through the countries doing this until we reached the sea. Then, when the crops are harvested, the dearest plants transplanted, and everyone high and safe, we'd board off the sides and fill the inside with cement to stabilize everything. The low countries would now be the high countries, and would survive the highest sea rise possible.
Expensive, for sure, but I think if national survival were ever on the line, they'd find a way. Also, I think the highness would form a tourist attraction.