4 Best Sights in County Clare, Galway, and the Aran Islands, Ireland

Even if you have only a few hours to explore Inis Mór, rent a bike (next to the pier) and head straight for Dún Aengus (or Dún Aonghasa.) Set at the edge of a 300-foot precipice towering over the ocean, this semicircular fortress is one of the finest prehistoric monuments in Europe and the main draw to Inis Mór. The purpose of its construction more than 3,000 years ago is a matter of conjecture, and also irrelevant to the legions of seabirds who occupy its scenic Atlantic perch looking out on Connemara and the 12 Pin Mountains. Beware: there is no barrier to the 300-foot drop at the edge. Allow 1–1½ hours for a visit.

In order to protect this fragile monument from erosion, you should approach it only through the visitor center, which gives access to a 1-km (½-mile) uphill walk over uneven terrain—wear sturdy footwear.

Kilmacduagh's 110-foot-high Round Tower, reputedly the tallest in the world, tilts 3 feet from the vertical over the monastery below. Arguably more impressive than the famous tower at Glendalough and without the backdrop of tour buses, Kilmacduagh is peaceful apart from the mournful lowing of cattle. The monastery was founded in the 7th century, but the tower, cathedral, churches, and abbot's home were built more than three centuries later. St. Colman, who founded the monastery, is buried behind the cathedral. Lying on his grave is believed to relieve back pain. The key to the site can be obtained across the street at the Tower View Guesthouse with a €5 deposit.

There are several stone forts in the Burren thought to have been in use between AD 400 and 1200, but Caherconnell—1 km (½ mile) south of Poulnabrone—is the best preserved, and the only one excavated and easily accessible to visitors. The interpretive center has an audiovisual display on the chief archaeological features of the area, including burial places marked by dolmens or cairns. Ongoing excavations continue to fill in the blanks of this impressive structure's history. Be sure to check out the sheepdog demonstrations and café.

This prehistoric hill fort, once populated with the most powerful chieftains in the region, is the largest of its kind in Ireland. It commands a sweeping view of the Shannon, Ireland’s longest river, which made it a strategic outlook for enemies navigating the main transport artery into the region. Today, a series of sturdy concentric walls set into a deep hilly thicket that hugs the northern territory of Dromoland Estate are what remain of this former dynasty's stronghold, constructed around 1000 BC. Information markers guide visitors past significant landmarks over the 27 acres, and a stone tower at the summit of the hill offers a rewarding view over the countryside. While much of the experience here is in your imagination (as in, imagining what would have once taken place on this very ground), the site makes for a truly beautiful and serene woodland walk, and it is particularly attractive in early autumn when the oak, horse chestnut, and beech trees turn every shade of crimson and amber.

Turn to the left on leaving Mooghaun, and heading toward Quin, cast an eye over a humped-back bridge. It was the site of Europe’s greatest gold find, many pieces of which are on display in Dublin and at the British Museum in London. The hoard belonged to the residents of Mooghaun.