A liquid storage portion for an aerosol-generating system includes a container configured to hold a liquid aerosol-forming substrate. The container has an opening for dispensing the liquid aerosol-forming substrate, and includes at least one transparent wall portion, such that the liquid level in the container can be visually monitored by the vaper. The container is further configured such that the liquid aerosol-forming substrate is held in a contiguous volume area of the container. The aerosol-forming substrate in the contiguous volume is confined near the dispensing opening of the container without regard to the orientation of the liquid storage portion.