From Rodoscycling hire shop follow the busy, ugly main coast road (*rat-run variant possible) southwest to the junction with Ikaron, (just before the Castle at Kremasti) and turn left here, following this to the fork. Bear right here and go straight on (for around a kilometre) to the next crossroads. Straight on southwards, (or going left on Epar. Od. Pastidas and second left to the village for a drink in Pastida) until the Y-junction with the road from Pastida. Straight on (i.e. bear right) for @ 200 metres and take the next track road off on the left, ignoring side junctions for around 1 km till you emerge back onto the main road to Maritsa (Epar. Od. Pastidas - Messanagrou). Turn left (effectively straight on) on this road and then keep on the main road (going right at the Y-fork onto the unclassified road/track also takes you into the village) and at the next fork bear right for Maritsa.
Length is given as 10.8 miles, with a steady well-graded climb into the hills from Kremasti to Maritsa. Highest point is Maritsa at 125m asl, steepest gradient is 3.9%, 156 metres of ascent and 50 of descent.
To extend the route to Psinthos. Head south on Pastidas - Messanagrou road (looking for the monastery on the left hand side?) winding past Alexandros Panorama and wiggling up and down through the hills to Psinthos.
There is a variant* possible avoiding the main road if you turn off right from the coast main road just at Leonidas Confiserie: on a side street or probably rough track? (shown on Google maps but not cycle.travel) called "Timokreontos". Check feasibility!
Keep left at the T-junction at the end, following Timokreontos, and then swing immediately right - this is the unclassified coast track "Pappaflessa" which tracks the sea. At the Labranda Blue Bay hotel the track bears to the left passing the hotel on the RHS. Matoula hotel is on the LHS. Swing round right, keeping to the right past "Sunny" discount shop on the left. This takes you back to the seaside track. Follow this to Paralia Kremasti beach and just before the tennis courts, turn left onto Niriidon track/street. Pass the "Black Rose" hotel and suites, keeping on Niriidon till it emerges back onto the main coastal road. Turn left here and immediately right onto Ikaron - the main route to Maritsa.
Note - if the Pappaflessa track is unfindable or unsuitable you can turn off the main road at a side road beside "Aegean fish" shop - there is a sign for the "Blue Bay" hotel at this junction. Cycle.travel shows "Zorba's cafe" at this track.
Follow this road past V&K supermarket to the T junction at the end, turn left and ignore the dead end on the first right, ignore the second right - it takes you to the Blue Bay hotel - but turn third right past the "Sunny" discount shop to access the coastal track. This track is shown on cycle.travel's website. Doing this route adds 0.8miles.
