The 9th Einstein Telescope Symposium took place in the center of the European Gravity Observatory in Cascina, near the VIRGO gravitational wave detector, on 19-20 April 2018. At the conference, among the over 100 participants also APEC and LIGO were represented at the highest level. On the first day, plenary speakers reviewed the scientific potential, technological background and the process of strengthening European cooperation on the third generation gravitational-wave detectors, including discussing the specific conditions for submitting the basic document necessary for the release of the ESFRI 2020 list. On the second day, the invited representatives of the possible sites of the Einstein telescope presented their efforts. The delegates of Nikhef presented the joint Dutch-Belgian-German site in Limburg, while the representatives of the Italian INFN introduced the site in Sardinia. The results of the preparatory work of Wigner FK and CSFK in the Mátra were presented by Mátyás Vasúth, leader of the Wigner FK Gravity Research Group. The symposium subsequently adopted a letter of intent declaring the launch of the Einstein Telescope Consortium and inviting interested researchers and experts to sign their agreement with the ET and their scientific goals.