The tiny whitewashed chapel of Agios Ioannis sits atop a 100-metre sea-rock on the northeastern coast of Skopelos, reached by 198 steps carved directly into the rock face. The climb takes about ten minutes and is straightforward if steep; the view from the top across the blue-green Aegean to the mainland is one of the finest on the island.
The chapel is genuinely old — a pilgrimage site for centuries — though it is now visited primarily by travelers who recognise it from Mamma Mia. This is fine; the setting justifies the trip on its own terms. The beach below the rock, Agios Ioannis Beach, is accessible by a short scramble and has clean, clear water. Come early in the day to beat the tour boats from Skiathos that arrive mid-morning with crowds in tow.