I do not really know of any country that allows to purchase real estate with cryptocurrencies, but you could always find a person that is interested in cryptocurrencies and that could be willing to do something like that however if the country in which you want to make that transaction only allows the fiat created by the government to circulate in the country then it is likely that you will need at first to sell your altcoins for fiat and then buy real estate with it.
Recently I participated in Bitdepositary bounty campaign and one of the utilities of their coin is to buy apartment and real estate. Recently, I got a message from their team that BDT coin can now be used to buy real estate in Dubai. If that's is true, I think it's welcome development in crypto world.