Somewhere on a rocky hilltop above the Torne river, a small mark in the stone once helped answer a very old question: how big, and what shape, is the Earth? Kerrojupukka is one of the points of the Struve Geodetic Arc, a chain of triangulation stations that stretches roughly 2,800 kilometres from Hammerfest in Norway to the Black Sea. Between 1816 and 1855, the Baltic German astronomer Friedrich Georg Wilhelm von Struve and his teams measured it, hilltop by hilltop, working with tripods, signal towers and an extraordinary patience, and the result was one of the most accurate measurements of the Earth's size and flattening made up to that time. Thirty-four of the surviving points, spread across ten countries, were listed as a World Heritage site in 2005. Sweden's share lies up here in the Torne valley.
The setting is Tornedalen, the Torne river valley, which runs along the border between Sweden and Finland, a land of birch and spruce forest, bogs, low rounded hills and slow wide water. Pajala is the nearest village, with about two thousand inhabitants and the fuel and food you will need, because the next services are a long way off. The Arctic Circle lies about seventy kilometres south, and in summer the sun hardly sets, while in winter the northern lights dance over the snow. The people speak Swedish, Finnish and Meankieli, the local Finnish dialect, and Pajala was home to the preacher and botanist Lars Levi Laestadius, whose revivalist movement spread across Lapland.
Riding here is about distance and emptiness. Roads are straight and good, usually quiet, with long views across bogs and forest. The danger is wildlife: reindeer and elk wander onto the tarmac, especially at dusk and dawn, and a collision with an elk can be fatal. Keep speed down, watch the verges and carry a warm layer even in July. Mosquitoes are legendary in midsummer, so bring repellent.
Local specialities include whitefish from the river, cloudberries in late summer, and leipajuusto, a squeaky baked bread cheese, served warm with jam.
The best season is June to August for the endless light, or September for autumn colours and quiet roads. Winters are brutally cold, with temperatures below minus thirty, and are for ice-roads and specialists. Climb the hill, find the marker if you can and imagine surveyors carrying brass instruments up here two centuries ago.