Archaeological excavation in an area of Lavrio (mining area from ancient times) has revealed ancient metallurgical installations which offer valuable information on this activity at those times. Within this context, a combined geophysical investigation was carried out in a place near Keratea City to find out whether there are additional installations apart from those that have already been revealed in the immediate area. More importantly, the objective was to locate the ancient tanks which provided water to the installations. Archaeological and geological information have helped in the design of the survey. EMI method measuring apparent conductivity was used to cover the whole area of investigation. Conductivity maps in various investigation depths have positioned the tanks and stacked first derivative maps in two directions (the two directions of the revealed walls) show covered walls. The EMI survey has indicated the position of three (3) ERT profiles made with the dipole–dipole array, which presented the ancient tanks with great detail in depth. GPR profiles for the detection of walls were noisy with the coarse material surface layer but the interrelation with ERT and EMI results confirmed the detected features. •Integrated geophysical survey to detect buried ancient tanks for water and walls•The ancient installations for metallurgical processing in Greece•Stacked directional 1st derivatives of EM data to detect linear objects•Combined interpretation of EM-ERT, EM-GPR and ERT-GPR data-results