Have you ever had sun tea? You get a clear glass container, preferably the kind with a nozzle for dispensing drinks from, then you fill it with water and load it up with a bunch of tea bags, maybe 10 per gallon(?), then you close the lid and set it somewhere in direct sunlight in the morning on a hot summer day. By mid afternoon you can take the tea bags out and put the tea container in your refrigerator.

It's just as dark as regular tea, but it has a smoother flavor. Typically you drink it iced, since it's a summer drink for hot days.