Several options for the GTC (Gran Telescopio Canarias) installations have been evaluated. In particular, different dome types and distribution schemes for the support areas to be incorporated in the installation have been assessed. In order to select the dome type, a technical-economic study has been carried out, in which the most important parameters that determine the efficiency of the dome during its life- cycle have been qualitatively and in some cases quantitatively evaluated. This paper presents a compilation of the evaluation process followed for the selection of the GTC dome and the establishment of a general layout for the location of the support areas.