This dream of mine may well seem ridiculous (perhaps I read too much populous Sci-fi in my youth) but please bear with me.
There are vast areas of the earth which are uninhabited or very sparsely populated eg cold deserts, hot deserts, arctic regions, mountains, deep seas. These areas are just left alone because they are valueless UNLESS some high value commodity - oil, plutonium, gold - is discovered. Then quickly, with human ingenuity, settlements are established and maintained - at least as long as the 'Gold Rush' lasts.
Science Fiction and Fact is rife with plans for the establishment of bases and colonies on other planets/moons, with technology providing climate controlled domes and underground areas where crops can be grown and a reasonable life style maintained. If these developments can be realistically contemplated on far distant planets, then surely they are achievable here on earth. There are historic examples of underground cities, mountain kingdoms, irrigation making the deserts bloom. We already have submariners living for months under the sea, workers living on platforms in the middle of the North Sea, established research stations in the Arctic and Antarctic. With the development of wind and solar power, communications, air freight - it is no longer necessary to establish road and rail infrastructure over vast distances. Hi-tech industries, financial businesses could flourish anywhere given a skilled workforce, likewise Holiday Resorts which in the main would require a less skilled workforce. There would also be a need for support services, builders, teachers, the whole range of occupations. It would not be my choice to live in an 'artificial' environment - I get claustrophobic in a shopping mall - but a town like that would suit many people and must offer a better life than being trapped in a war torn country, or shanty town beside an overcrowded city.
That, in a nutshell is my dream. The UN to take over these valueless empty areas, use the overseas aid budgets to develop essential infrastructure, then open the doors to refugees and economic migrants alike. This would relieve the pressure on overcrowded countries, cities, whilst providing the opportunity of new start for what we used to call 'displaced persons'.
Feel free to pick this concept to pieces if you will, but can you come up with a better idea?