"Depending on design, multilevel burial chambers can accommodate 20 to 40 times more plots than conventional cemeteries of the same size," said Israel Lin of the Technion's faculty of civil engineering.

"The number of levels possible is limited only by topography," he said.

The underground cemeteries would be designed as either circular rooms extending down 20 floors with elevator shafts up the middle and walkways around the perimeter, or as long corridors with burial plots in the walls, the Technion study recommended. Both would be well-lit and visually appealing.

Burial caves would be designed in accordance with the Talmud, which provides detailed instructions on how to build these burial sites.

Underground cemeteries are especially suited to cities atop hills, such as Jerusalem, Haifa and Tiberias, Lin said.

They could be placed directly under cities and the areas near the burial chambers could be used "for parks, buildings, industry, whatever," unlike conventional cemeteries where the land is not usable, he said.

These sites could also serve as shelter in case of nuclear or biological war since they would be built down into existing rock. They would be deeper and stronger than existing bomb shelters, Lin said.