I visited this WHS in June 2016. I drove from Ironbridge and I arrived just before the last few boat trips which float through the Pontcysyllte Aqueduct marketed as the river in the sky. The boat trips' highlight is obviously the unique crossing over the aqueduct and the feeling of unease while standing to take pictures at a height of 38 metres (there are no safety railings on one side!). Another worthwhile boat trip experience at the Llangollen canal is the horse drawn boat trip should you have more time in the area. After visiting the Trevor Basin Visitor Centre (open 10am to 4pm), I enjoyed the heritage trail and after a quick photo of the bilingual UNESCO plaque in English and Welsh I drove to the nearby Chirk aqueduct before heading towards Harlech. This WHS reminded me of the Vizcaya Bridge in Spain and both were worthwhile WH visits. I look forward to visiting Forth bridge soon as well as the nearby river Clyde!