Rathcroghan

Rathcroghan is the royal site of Connacht, the counterpart of Tara in Meath, and in the literature it is Cruachan Ai - the seat of Medb, from which the army of the Cattle Raid of Cooley sets out. On the ground it is a complex of around 240 monuments spread across six square kilometres: barrows, ring forts, linear earthworks, a huge mound about ninety metres across, and avenues. Almost none of it has been excavated, and geophysical survey has found far more beneath the surface than is visible. Oweynagat, the cave of the cats, is a narrow natural fissure with a souterrain entrance built partly of ogham-inscribed stones; in medieval texts it is described as an entrance to the otherworld and the origin of Halloween's associations. Everything is on working farmland in multiple private ownerships, so the visitor centre at Tulsk and its guided tours are the practical way in.

What you actually see

• The great mound - about ninety metres across, the site's focal monument.
• Oweynagat - the narrow cave with ogham stones in its entrance.
• The monument spread - around 240 sites across six square kilometres.
• The Tain connection - the seat of Medb in the Ulster Cycle.

When to go

April to October. The centre and tours are the only reliable access; monuments are on private farmland. Oweynagat requires a guided visit, boots and a torch.

Honest expectations

Most monuments read as low grassy mounds - this is a landscape for the informed rather than a spectacle. Oweynagat is a tight, wet, muddy crawl and is not for the claustrophobic. Access without a tour is limited by private ownership.

Nearby

Roscommon town is south; Boyle and Lough Key are north.