Where can I find an efficient R-Tree implementation?

Question

I'm looking for an R-Tree implementation, in C, Objective-c and even C++, which shall be efficient for searching the 2d rectangle in which a point falls ( memory efficiency would also be great, but I can sacrifice a bit more memory for time even while I am on an iPhone ). A good documentation will be appreciated too

Answer 1

Check out this page, it provides implementations (in C, C++, Java, etc.) for several variants (R*, R+, etc.).