County Cavan: See
Cavan County Museum is in Ballyjamesduff.
Dun A Ri Forest Park is in Kingscourt.
The Workhouse Museum is within the shell of a grim institution in Bawnboy, northwest of Belturbet.
Upper Shannon: Ireland's great Mississippi arises at Shannon Pot, reached by a short hike from the car park on R206 above Corbeg in the northwest of the county. It flows southwest to enter County Leitrim at Dowra, then down into Lough Allen, see Drumshanbo. That lough is the upper limit of navigation on the Shannon.
Drumlins, hundreds of them. They're little ridges or hillocks, slightly elongated, in groups aligned the same direction. They're typically 500 m long by 200 m wide and are composed of clay, gravel and boulders deposited beneath glaciers. They form a "basket of eggs" landscape, and when flooded by sea or lakes they form a scenic pattern of islands. They're found worldwide but especially in a broad belt from Clew Bay in County Mayo to Strangford Lough in County Down, and indeed their name is Irish: droimnín, "littlest ridge". Cavan is the centre of this drumlin belt and they define its landscape. Their sparse, boggy soil is unsuitable for arable farming or even forestry so they're mostly just rough grazing land, but as islets they create a platform for hermit's dwellings, forts and wildlife refuges. This particular drumlin belt was laid down 13,000 years ago, at the retreat of the last Ice Age in Ireland. Precisely how they formed is debateable: by simple deposition, by scouring away of surrounding material, by flood action? Study of modern glaciers suggests a mix, but in County Cavan you'll have many a happy idle hour to contemplate the question.
Limestone terrain by contrast forms the northwest of the county, around Blacklion. Admire it both above ground, as at Cavan Burren Park, and below in the Marble Arch Caves.