Regarded through a certain lens, Athlone is Ireland’s answer to Budapest, the US’s Twin Cities, Minneapolis-St Paul, or Osgiliath and Minas Tirith in The Lord of the Rings. It is, to put it another way, a major urban settlement that began as two separate towns either side of a river. That divide endures to this day. Roughly one-fifth of Athlone is in Connacht, the rest in Leinster. And of course, the river running down the middle is the mighty Shannon, perhaps the only body of water in Ireland to truly capture the imagination and enjoy an outsize significance in the emotional hinterland of the nation. We don’t generally get too bothered about rivers or indeed bodies of water in general. The Shannon comes close to being an exception.Athlone is, thus, a place ripe for discovery and celebration. That is the mission undertaken by the very watchable first instalment of the returning Building Ireland (RTÉ One, 7pm). We learn how Athlone began as a strategic crossing and how the old town walls, which endure to this day, marked it out as a place worth both defending and conquering.At just half an hour, the episode only skims the surface of Athlone’s history. It isn’t a deep dive into this crossing of the Shannon, and it also doesn’t pretend to be. Instead, it has a roving, bustling energy and benefits from the enthusiasm of its presenters: geographer Dr Susan Hegarty, engineer Tim Joyce and architect Orla Murphy. We visit the ruins of a grand Jacobean house from the early 17th century and walk the town centre, where the narrow, winding streets are a testament to their medieval origins.There is also a segment on Athlone’s uneasy relationship with the Shannon – the gateway to the east and west, but also a cruel mistress which has brought terrible flooding across the decades. That said, there is the occasional tendency to use ivory tower academic jargon. At one point, for instance, we are told the town is “re-engaging with its riverside context with confidence” – a sentence which could have done with being translated into English.Yet that is ultimately a quibble. This engaging series hits its stride when the presenters are pounding the pavement, admiring the views and celebrating the Irish urban landscape for what it is: sometimes worse for wear, often just about hanging together – but, in the end, like nowhere else in the world.