The Temple of Behbeit el-Hagar is one of the Nile Delta's great archaeological might-have-beens: a once-imposing temple of Isis now reduced to enormous granite blocks scattered across the village edge. The ruins are fragmentary, but the scale of the carved stone makes clear that this was no minor shrine.
It is a specialist stop rather than a polished monument, and that is exactly why it can be rewarding. Go with realistic expectations, preferably with a driver who knows the Delta roads, and combine it with Mansoura's own historic houses and markets.