Nanoscale variations in the electromagnetic environment strongly influence quantum emission processes, yet direct quantitative visualization of these effects at the single-emitter level remains challenging. By combining single-molecule super-resolution microscopy with time-correlated single-photon counting (TCSPC), we read the local electromagnetic environment of each molecule from its position and its excited-state lifetime. Using wafer-scale arrays of hollow plasmonic nanocones, we map position-dependent variations in the local density of optical states (LDOS) along the nanocone axis. We observe pronounced LDOS gradients that evidence a shortening of the fluorescence lifetime from nanoseconds to few picoseconds. The measured decay rates along the nanocone axis with maximum value at the top ring, yielding a total spontaneous-emission rate enhancement of more than two orders of magnitude at the single-molecule level, reaching an enhancement of the total spontaneous-emission rate of up to two orders of magnitude at the single-molecule level, in agreement with numerical simulations. These results provide direct experimental access to three-dimensional electromagnetic landscapes and establish a non-perturbative platform for quantitative molecular nanosensing in complex photonic architectures. The approach opens new opportunities for engineered room-temperature photon sources, vectorial field sensing, and scalable integrated nanophotonic technologies.