Most visitors come in by air. Ronaldsway, the Isle of Man Airport, sits two miles north, and buses 1, 2 and 11 each run hourly from Douglas down through the airport to Castletown, Port Erin and Port St Mary — collectively a service every twenty minutes for most of the day. The last bus is around nine, with a single late-night N1 just after midnight on Fridays. The other way in is the Isle of Man Steam Railway from mid-March to the end of October: four trains a day, forty minutes from Douglas, dropping into a Victorian station on the north-eastern edge of town. From there it is a five-minute walk along the Silverburn River to Market Square. The town has no working taxi rank of its own anymore — the local operator folded — but Castletown is so compact you mostly will not need one.

The streets around the castle are Georgian and Victorian, low and trim, with the Parade running along the harbour and Arbory Street sliding away inland. Old St Mary's on Market Square is the original Anglican church, now offices; St Mary's on the Harbour, on Hope Street, opened as a school in 1838 and was only consecrated as a church in 1989. There is a small Roman Catholic church, St Mary's and St Columba's, on Bowling Green Road. Behind the southern edge of town a Viking burial mound, forty-five feet across and six feet high, sits unexcavated. It is probably ninth or tenth century. Nobody has dug it up yet, and it is the sort of unannounced monument the Isle of Man specialises in — there if you go and look for it, otherwise simply a hump in a field.

East of the airport runway, the road slips around to Derbyhaven, once a significant port and now essentially a Castletown neighbourhood. From there a single causeway runs onto Langness Peninsula. The Castletown Golf Links spread across the dunes — 6,431 yards from the white tees, par 72 — and a side road branches across to St Michael's Isle, also called Fort Island, a bird sanctuary that holds the ruins of Derby Fort (an artillery position of 1645) and the small twelfth-century St Michael's Chapel. The southerly tip of Langness has a daymark on a low rise and a lighthouse at Dreswick Point, the most southerly point on the Isle of Man's main island. You need your own wheels for any of this — the buses do not run out here. The reward for the drive is empty cliffs, wheeling fulmars, and views back across the bay to the castle silhouette.

Provisions in town are the two basics: Coop Food on the Parade by the castle, and Shoprite on Arbory Street. For a drink at the end of the day, The Sidings sits right at the railway station, taking its name from the line it backs onto — open Sunday through Thursday from 11:30 in the morning until 11, with Friday and Saturday running on to midnight. Knock Rushen House is a small B&B on the southern edge of town near the Viking mound. The Southern Agricultural Show in late July, half a mile south of Fairy Bridge, draws the southern parishes for a weekend of livestock, tractors and shouted commentary, and is as good a window into working Manx life as a visitor will get.

Douglas, the present capital, is the island's transport hub and where most of the museums and concentrated sights are. The same buses that brought you down to Castletown will take you back up. South of town, Port St Mary keeps a smaller harbour, with boat trips out to the Calf of Man and on to the breeding seabird colonies. Cregneash, the National Folk Museum, is a short ride west. Anywhere you go from here you are within thirty miles of where you started — the Isle of Man is that kind of country — and you will probably pass Fairy Bridge on the way back to the airport. The buses make an announcement reminding you to say hello to the fairies as you cross. It is not really a joke.