Barmouth bridge stands as one of the most recognisable sights in the town - the bridge marks the arrival of inland tourists as they finish snaking their way up the Mawddach river and arrive at its mouth. For many this old rail bridge marks the beginning of holidays and good times to come, but surprisingly not many people take the time to explore the bridge. It first opened in the 1860's and has been an active train line more or less constantly ever since, surviving two world wars, multiple closure threats and has since earned its Grade II* Listed status. The bridge's distinct twin arches actually can facilitate the passage of ships, with the first of the arches (closest the Barmouth side) rotating on it's central support - unfortunately this feature is not used any-more, but would be an amazing thing to see. A footpath allows pedestrian and bicycle access with a small honesty toll for crossing and I will run you through getting to the bridge and what you can expect to see.
Reaching the bridge is unfortunately a little challenging from the Barmouth side, it currently lacks any dedicated walkways and the road you will need to cross is littered with blind-spots. In its current form I would not regard the bridge as being particularly disability friendly from the Barmouth side and I would take great caution with getting young children and dogs to cross the road. The organisation Barmouth - Viaduct Access Group have been pushing for safer and easier access, you can view their progress on their website and sign up for updates.
In order to reach the bridge, follow the main-road out of Barmouth past The Last Inn and up the hill - the road only has a walkway on one side and unfortunately this is the opposite side to where we need to be. The entrance to the bridge is both signposted and easy to spot but it sits on the outer edge of a fairly blind corner (See map reference: 52°43'12.0"N 4°02'49.1"W): with two people acting as spotters you can cross fairly safely but even then you're still taking your life into your hands. Thankfully the speed limit in this area is low and the roads make it difficult for drivers to speed but regardless do take extra caution when crossing here. A second possibly preferable option, is to cross the road into a small walk area before the bridge; as you approach the bridge entrance there are two large stones on the opposite side of the road, between these is a small entrance at a point where it is slightly easier to cross (Street View Reference), cut through here and you will come out about 10 yards up from the bridge entrance - you will unfortunately have to walk up the roadside if you take this option but it is probably a safer considering the alternative. Once you have made it across there is a surprisingly steep slope down to the bridge itself and if you follow the paths down to the left you can get onto a nice little soft-sand beach with beautiful views of both the bridge and Barmouth Harbour.
The Fairbourne approach is a longer walk but much simpler - all you need do is find your way onto the footpaths that run alongside the estuary (one example entrance is here towards the beach car-park but more entrances may be littered around the town) and follow it inland until you reach a pedestrian rail crossing. After safely crossing the railway head north, away from the platform, to reach the bridge. If needed, public toilets are available by heading in the opposite direction after the railway crossing, past the platform.
So now that you have arrived your exploration can begin, the bridge offers spectacular views in every direction and it is definitely worth planning your walk so you experience them at both low and high tide. At the Fairbourne side you can access the underside of the bridge by passing over a turnstile and following the beach underneath; at low tide you can explore a great distance around the bridge but you'll need appropriate footwear and to keep an eye on the tide. The boards that make up the walkway occasionally have gaps and may move underfoot so if you have any issues with water or heights it is probably best not to look down. Finally, a couple of warnings: the bridge is very exposed so make sure you have appropriate clothing for the weather and take it steady in strong winds. Secondly, a train may pass while you are crossing and it may be both loud and fairly shaky on the bridge, so just hold onto the handrail, keep a close eye on dogs and children, and wait for the train to pass.
Once you're done exploring the bridge you have plenty of options for adventures beyond the obvious towns and beaches nearby. On the Fairbourne side, you could head on to Arthog to see the falls there and even carry on up the hills to see the stunning Cregennan Lakes. On the Barmouth side, you could head up Dinas Oleu to see the Frenchman (See National Trusts information here), The walks around both sides of the estuary have options that could take you for miles and miles so get your boots on and get exploring!