Notice that during this entire process the specific volume of the water increased by more than three orders of magnitude, which made it necessary to use a logarithmic scale for the specific volume axis.
We can repeat this same experiment at different pressures to attain more curves as shown in the figure below. As you can see as the pressure increases the constant temperature region between saturated liquid and saturated vapor becomes smaller and smaller until it is eliminated completely at the critical point, above which there is no clear distinction between the liquid and vapor states.
Saturation lines can be drawn by connecting the loci of the saturated liquid and saturated vapor points as shown in the figure below.