If the land is taxed then you must find a renter willing to pay more than your tax, otherwise you would sell. Meanwhile renters will search for the lowest rent, which is naturally found in high density areas. So cities would still form, and the vast tracts of unoccupied land would be money-losing assets that must be abandoned, at least until population growth makes some of those plots profitable. The market would fluctuate with supply and demand, just as it does today.