Boat trips from Skradinski buk head up the river into the so-called Visovac Lake, a stretch of the Krka which measures 800m from shore to shore at its widest points. Grey-green hills rise steeply on either side. Main destination for the excursion boats is Visovac Monastery, picturesquely located on an island 7km upstream from Skradinski buk. A Franciscan foundation has existed on this site since at least the 14th century, although the church we see today was built in 1576. Long a centre of Catholic Christianity in the region, it nowadays holds a seminary, as well as being the site of a much-visited church. A decree issued by Ottoman Sultan Mehmet IV, returning Visovac to the Franciscans in 1674, is held in the monastery treasury. Upstream from Visovac, the ruins of Kamičak fortress can be seen on the cliffs above the eastern shore. Again built by the Nelipić family in the 13th century, it was demolished by the conquering Ottomans after 1522.