This stamp from Monaco was issued in 1961 for the UNESCO Campaign to preserve Nubian monuments (Scott #479).
It has two interesting features. Firstly, there's the fact that it is meant to be displayed as a diamond shape rather than a plain old square. Secondly, it depicts a less common subject of all the Nubian monuments stamps I've come across: a submerged sphinx of Wadi es Sebua, the Valley of the Lions.
The Ramses-headed sphinxes line an avenue leading to the Temple of Amun-Ra, built by Ramses II in his 44th year of rule. The construction is similar to that of the temples of Abu Simbel: a free-standing facade and rooms hewn from the surrounding rock (speos).