  We have examined the giant radio galaxy 3C~236 using LOFAR at 143 MHz down to
an angular resolution of 7", in combination with observations at higher
frequencies. We have used the low frequency data to derive spectral index maps
with the highest resolution yet at these low frequencies. We confirm a previous
detection of an inner hotspot in the north-west lobe and for the first time
observe that the south-east lobe hotspot is in fact a triple hotspot, which may
point to an intermittent source activity. Also, the spectral index map of 3C
236 shows that the spectral steepening at the inner region of the northern lobe
is prominent at low frequencies. The outer regions of both lobes show spectral
flattening, in contrast with previous high frequency studies. We derive
spectral age estimates for the lobes, as well as particle densities of the IGM
at various locations. We propose that the morphological differences between the
lobes are driven by variations in the ambient medium density as well as the
source activity history.
