A nationally important natural feature, the Suurisuo mire complex is located in Janakkalas and is one of Tavastia Proper's most important mires. Suurisuo boasts impressive natural diversity, with thousands of endangered plant and insect species found here. Visitors can climb up Suurisuo's birdwatching tower to look out over the mire and birds nesting in its groves. The tower can be reached from the parking area off of Leppälammintie, following a signed nature path.

UPM corporation is the landowner of Suurisuo's 232-hectare Natura area. Suurisuo is an important education, research and hiking destination, which has been used by, for example, the University of Helsinki in its teaching since the 1970s.