I don't think it would really be that hard to solve this from an engineering perspective (see for instance how the Brooklyn bridge was built) its just that anyone with enough money and sense to solve the problem properly is probably to smart to get involved with what IMO is likely a hoax that got out of hand.

Not really. Not to get into politics, but the Israeli army is currently trying to find the tunnels from Gaza and haven't figured out a great technical option - and those are hollow spaces. In this case you are trying to pick out solid objects from other solid objects, that is tough.

Sounds like you should raise money and launch your own expedition.

Let's kickstart it! We can feed the team with potato salad.

IIRC, ground penetrating radar has poor performance in clay or generally wet soil, otherwise it would probably have been done already as the technology has been somewhat widely accessible since at least the 1980s.

You're looking for ground penetrating radar http://en.m.wikipedia.org/wiki/Ground-penetrating_radar.

I often wonder. It seems that our technology must suck at this or is simply too expensive to use.