From "A Pocket Guide to Carthage"

Built roughly 3000 years after Carthage's fouding, The Pyramids tower over the plains to the East of the city proper. Constructed of stone overlaying an intricate lattice of ancient wood harvested from what are believed to be extensive forests that surrounded Carthage for the first two millenia of its existence, the six four-sided structures are laid out in an inverted "L." The noted early geographer, Basil Gruene (436 - 483, NCE) was the first to point out that the pyramids exactly echo, at a smaller scale, the positions of the six peaks of the Curtain Range Northeast of Utica. Why this would be so, and the original purpose of these mammoth wonders of early engineering, remains unknown.

That hasn't, however, stopped an entire industry of speculation from growing around the site, and the street hawkers on the Avenue of Wonder will be happy to invent any answer you wish to hear--for a price, of course. For the more scientifically inclined, tours of The Women's Tomb are available each day at 10:45 AM ($6 cC Adults, $2 cC Children 4 to 14): gather by the blue obelisk in the Women's Courtyard, South of the largest pyramid (reservations recommended). Tours may also be arraned on an informal basis with the locals who hang around the Memorial Square (see map). Look for the grey scarves worn by potential guides. Prices will vary, but if you negotiate well, a group of six should receive a three hour tour for under $8 cC.

The Pyramid Museum and Research Institute of Carthage (PMRIC) (10:00 AM to 10:00 PM Daily, closed National Holidays. $5 cC Adults, Children Free) remains the best source of information on the Pyramids, and a visit to their public exhibit behind the two Northern Pyramids is strongly recommended. Here, you will find historical information on the Pyramids, as well as the requisiste gift shop. Children will find hands-on activities, including a replication of the process used to age and strengthent the wood and a presentation on the forests believed to originally surround Carthage.

(from http://civisibiles.blogspot.com/ )