A man emerges from a telephone booth that was turned into a mobile saunaPhotograph: Markku Ojala/EPAA man fuels up a Datsun Finn rally car-saunaPhotograph: Markku Ojala/EPAA couple kiss in a cosy saunaPhotograph: Markku Ojala/EPAA combine harvester that has been turned into a mobile saunaPhotograph: Markku Ojala/EPAThere are just two rules for the saunas: they have to be mobile, and they have to fit at least one person insidePhotograph: Markku Ojala/EPAA view inside a mobile saunaPhotograph: Markku Ojala/EPAA man holds 'vihta', a bunch of leafy birch twigs that is a traditional washing implementPhotograph: Markku Ojala/EPAThe 'horse' that pulls this sauna is really a scooterPhotograph: Markku Ojala/EPAThe festival has grown since 2006, when just 18 saunas were on displayPhotograph: Markku Ojala/EPASome 6,000 visitors visited the festival, doubling the population of Teuva for the weekendPhotograph: Markku Ojala/EPA