The formation of a 7×7×7 nm3 size GaAs quantum dot (QD) at the intersection of three quantum wells is demonstrated for the first time. Intense radiative recombination between zero-dimensional states in the QDs is clearly identified by microscopic photoluminescence ( μPL). In contrast to the inhomogeneously broadened quantum well and quantum wire signals originating from the complex twofold cleaved edge overgrowth structure, the strongly spatially localized QD response is characterized by spectrally sharp lines in μPL excitation spectra with a linewidth below 70 μeV.