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People living more than three thousand meters above sea level find it difficult to raise vegetables all year long. People living in the highlands of Peru and Bolivia， for example， cannot grow vegetables outdoors during the months of May through September. It is very cold in the highlands at that time of year. If traditional farming methods are used， vegetables will not survive.

However， there is another way to grow vegetables throughout the year in cold areas. It is a method of gardening developed by a private agency called World Neighbors. The method uses “hot houses” built below ground. A hot house is a building covered with plastic or glass in which vegetables or flowers are grown. The traditional hot house is built above ground.

The air temperature is cold in the highlands of Peru and Bolivia during the winter. But， the winter sun is hot. So， World Neighbors advises farmers there to build hot houses below ground. The design is simple. The material does not cost much. Here is how World Neighbors says to build it： Dig a hole two and one-half meters wide and six meters long. Make it about two meters deep. Build wall with a door in one end of the hole. Dig steps from the ground down to the door.

Now， build a wall along the top edge of the hole. Make it about one-half meters tall. Earth bricks work fine. Build two shorter walls on the ends.

These will be uneven; one side will be as high as the existing wall. The other side will be at ground level. Leave a small opening in each of these sloping walls. This prevents the hot house from becoming too hot. Now， make the roof. Build a wood frame. Cover it with clear plastic. Connect it to the brick walls.