Lost technologies

The gigantic stones used by Herod for the Temple and supporting walls (Western Wall) and the Cave of the Patriarchs were smoothd and squared to such a degree that no mortar was necessary.

Egyptian brain surgery during the time of the Pharoahs

The calculations required for the Mayan calendar

Claculations necessary for the placement of the gigantic stele at Stonehenge

I've always heard of an ancient race had the ability to make glass flexable and thin as a sheet of paper without breaking. You copuld bend and flex and the glass and it wouldn't break. This is not plastic I'am talking about. Maybe they were from KPAX. 

There was an ancient Chinese artistic technique that was banished in the Ming Dynasty.

The last surviving piece was dubbed "Brown Spots on the Wall".

It was destroyed, but the artist's name was:

Hoo Flung Pooh.

From Egypt, I can say time-telling using the sun dial is a lost technology.