I have a "Secret Garden" in a storage room in the basement of my house. It's currently a hydroponics system growing leafy greens and herbs. You can see an hourly photo of it below:
Click the above photo for a larger version.
There's usually kale, spinach, cilantro, parsley, and green onion growing. Sometimes dill and basil.
Nutrient Film Technique
The garden uses nutrient film technique (NFT) to continuously deliver a shallow stream of nutrient solution to the plants growing in 2" ABS pipe. A submersible fountain water pump sends nutrients up 1/4" irrigation hose to each of the four pipes. The nutrients flow down the slope passed all the roots and return to the ~40 L reservoir. An air stone oxygenates the water. Two computer case fans ensure adequate airflow.
The nutrients are kept in a reservoir underneath the towel, which helps block light and limit algae growth:
Previous Garden
My previous system Helios Alpha could grow up to six plants. It's designed around a single 102 L plastic tote. It holds enough water to harvest lettuce once before refilling. After the initial setup, the system can be ignored for weeks.