The great hulking shell of this burnt-out, 14th-century Cistercian monastery practically insists on exploration. Stairs lead up into the ruins, where you can wander around the masonry and climb to the top of the tower for views stretching for miles over the flat countryside. The former church still has its roof and Gothic windows, and even in its derelict state it's easy to imagine how grand it must once have been.
The land was given to the Cistercian order in 1220 in gratitude for its role in converting the Estonian pagans following the Christian invasion, but construction of the monastery didn't start until 1317. If you're thinking it looks more like a fortress than a place of worship, it's for good reason. Relations with the enslaved Estonian populace were shaky, and during the St George's Night Uprising, locals attacked the monastery, killing 28 monks and burning it to the ground.
The monastery was rebuilt and reached the height of its powers in around 1480. In 1558 it was seized by the master of the Livonian Order, who turfed out the monks and strengthened the fortifications. During successive wars it changed hands several times and was further fortified, before being converted into a manor house in the 17th century. A lightning strike in 1766 set it alight once again, and it was finally abandoned, the stones being used to build neighbouring Padise Manor.