  Gas detector are very light instrument used in high energy physics to measure
the particle properties: position and momentum. Through high electric field is
possible to use the Gas Electron Multiplier (GEM) technology to detect the
charged particles and to exploit their properties to construct a large area
detector, such as the new IT for BESIII. The state of the art in the GEM
production allows to create very large area GEM foils (up to 50x100
$\mathrm{cm}^2$) and thanks to the small thickness of these foils is it
possible to shape it to the desired form: a Cylindrical Gas Electron Multiplier
(CGEM) is then proposed. The innovative construction technique based on
Rohacell, a PMI foam, will give solidity to cathode and anode with a very low
impact on material budget. The entire detector is sustained by Permaglass rings
glued at the edges. These rings are used to assembly the CGEM, together with a
dedicated Vertical Insertion System and moreover they host the On-Detector
electronic. The anode has been improved w.r.t. the state of the art through a
jagged readout that minimize the inter-strip capacitance. The mechanical
challenge of this detector requires a precision of the entire geometry within
few hundreds of microns in the whole area. In this contribution an overview of
the construction technique, the validation of this technique through the
realization of a CGEM, and its first tests will be presented. These activities
are performed within the framework of the BESIIICGEM Project (645664), funded
by the European Commission in the action H2020-RISE-MSCA-2014.
