How many of these bridges can you identify?   

Please choose which you feel is the ONE most obscure and tell us about it.
Sample answer - "I can identify 8.   Number 17 is Tucking Mill Viaduct which has a public right of way across it"

1. It has 21 arches, stands 30 metres tall and featured in four ‘Harry Potter’ books.

2. Tolls were collected for foot and cycle traffic up to 2013 but this has been voluntary since 2017.

3. The largest viaduct in Britain to be constructed of concrete blocks and has created a single track crossing approximately 800 ft long and 120ft high.

4. It opened in 1874 for a single track; in 1879 its width was doubled for a second track.  It is a scheduled monument, and is one of only two surviving railway bridges in the United Kingdom that use wrought iron lattice piers to support wrought iron trusses.

5. The viaduct consists of 16 spans of wrought iron, lattice truss girders, carried on 15 wrought iron piers which are not fixed to the ground but are supported by brick and ashlar bases.

6. While it was being constructed, the innovative low-rise arches of the structure attracted considerable criticism and controversy surrounding their alleged lack of stability; as a result, the centring for the arches was left in place until its destruction during a heavy storm in late 1839, yet the arches stayed up.

7. It has been claimed that it was officially opened by Queen Victoria on 6 August 1850, but she was reportedly so frightened of its height that she refused to travel across it and left the train, using a horse-drawn carriage to travel the length of the bridge on the ground.

8. The current bridge dates from 1902–3 prior to the doubling of the track. In a typical year, it is opened 1,300 times.

9. The bridge was designed by the chief engineer of the London and North Western Railway. It opened on 2 March 1863. It carries two tracks and consists of five 120 foot lattice girder arches set on stone piers.

10. Electrified with the (750 V DC^▸ (Direct Current)) third rail system and electric services commenced on 28 February 1926. Early electric services were worked by early Southern Railway 3-car Electric Multiple Unit trains often built from old SECR carriages.

11. The headroom is 10ft (3.1m) - not enough room for a coach, let alone a double-decker bus, but that doesn't stop drivers trying the impossible.  Now officially the country's most dangerous bridge, it was hit by over 130 vehicles in the 1990s alone.  A figure that includes one double-decker on 15 October, 1996 which Railtrack deliberately rammed into the structure at 40 mph to publicise the danger of this bridge in particular and low bridges in general.

12. Its unique design consists of two 455-foot lenticular iron trusses 100 feet above the water, with conventional plate-girder approach spans.

13. This extremely unusual type of plate girder bridge, which features very tall girders that have overhead bracing, forming a giant hollow tube of riveted iron. Several examples were built, however this is the only remaining example. It also was one of the first examples built.

14. It is still in use, being the oldest railway bridge in continuous use in the world. It is a Grade I listed building.

15. Carries a river across a railway line above a station, which was opened in December 1868.

I can identify four of them (I think)

I think six is the bridge over The Thames at Maidenhead

Think I can get four or five, No3 is Calstock Viaduct built when the line was extended from Bere Alston to Calstock and on to link with the East Cornwall Mineral Railway which ran from the quarries in the Callington area to Calstock Quay, reaching the latter by an incline.
When the viaduct was built it had a wagon lift down to the quay to service the lines of the East Cornwall Mineral Railway at the quay.

No2 Barmouth bridge

So we have ...

1 - Glenfinnan - BobM
2 - Barmouth - TonyN
3 - Calstock - bradshaw
6 - Maidenhead - Witham Bobby
15 - Sloane Square - PrestburyRoad

14 - Tanfield Arch?

(Sorry - amend to say to complete the required answer - before I read the answers above I think I knew were 1, 6, 7, 10, 12, 13 & 14. I think the Tanfield Arch is the most obscure simply because it receives remarkably little publicity for an important structure)

Or a play at the Royal Court.

I think I can put a name to seven of them but may not all be correct.

I thought at first no. 4 was Bennerley Viaduct with the description and the mention of it being a scheduled monument, but I wasn't aware of it having originally being single track.

In fact, I think no. 5 is Bennerley Viaduct.