This might be one of the longer walks and it's one of the most rewarding for anyone interested in industrial history. Gas Street Basin is where the Main Line (completed 1772) meets the Worcester and Birmingham Canal (1795) at Worcester Bar, a seven foot barrier which prevented the latter 'stealing' water from the BCN before a stop lock was introduced in 1813. The walk is circular taking in the Soho Loop, Smethwick Locks, Engine Arm and Spon Lane Locks before turning back to the City Centre on the New Main Line at Bromford Junction.
The Main Line originally ran further into the city centre to Old Wharf, Paradise Street, the headquarters or the BCN until 1912 but this arm has now been built over, and you start the walk by going under the Broad Street Tunnel and Black Sabbath Bridge, passing the ICC with the NIA (or whatever its sponsor's name is currently) in front of you. Then go left in front of the Sea Life Centre at Deep Cutting Junction with its unique island sign post and over the Oozells Street Loop at Old Turn.
From here this is a walk along the Birmingham Main Line (new and old) on either side of the canal towards Wolverhampton. So not to miss anything, the best idea is to take one towpath to Smethwick and then the other one on the way back. Leaving the swish apartments of the City Centre and Oozells Street Loop behind, look out for the 'Roundhouse' (1802) just after Sheepcote St. Bridge, a striking horse shoe structure, originally a warehouse and stables, now owned by the National Trust who have turned it into 'a hub from which to explore the city'. Passing Monument Lane Basin (a former LNWR railway interchange), you'll reach the start of Icknield Port Loop. This is one of the several loops that were part of the slow meandering Old Main Line built by James Brindley and subsequently by-passed by Telford's very much straighter and quicker New Main Line which was completed in 1827. The 8 acres of land that Icknield Port encompasses is undergoing massive regeneration but, until this is completed, dereliction and graffiti is unremitting as you approach the eastern end of the loop at the unique crossways at Rotton Park Junction.
At the junction take the Soho Loop and, after a fairly unpromising start if you're not an industrial archaeologist, there's parkland that's become a favourite location for fly tippers and a neat housing estate. On the far side of the canal, the area around and including the City Hospital is another part of west Birmingham being totally redeveloped to provide hundreds of new houses. At Hockley Port Junction, the Soho (or Birmingham Heath) Branch once served Boulton's Soho Manufactory, the world's first modern mass production factory (1766 - 1848), and several railway interchange basins at Hockley Goods Yard (Hockley Port). Trade ceased in the 1950s and it now accommodates a few boats. Further on, HM Prison Birmingham, better known as Winson Green, appears on the horizon and you pass the forbiddingly named Workhouse Wharf and Asylum Bridge which reference two other establishments (known as the Badhouse, Workhouse and Madhouse) that were once located on a loop that's 1¼ miles long before rejoining the main line.
Turning right, back onto the new main line by the railway sidings at Winson Green Junction, you'll pass the Gauging Island and then the disused Cape Arm (another part of the old line) on the other side of the canal. One notable factory on the Cape Arm was Fox, Henderson & Co.'s London Works where the metal framing was manufactured for the Crystal Palace and Great Exhibition of 1851. Subsequently the works were taken over by the company that became GKN. Opposite the Cape Arm is the southern end of the Avery Arm which is entered under a Horseley roving bridge, just a basin remains at this end that served Adkins & Nock Soap Works (the nearby railway junction was called Soap Works Junction), and later the Mond Nickel Co. When extant, the arm continued round to the Soho Foundry established in 1796. Now owned by Avery Weigh-Tronix, this was where Matthew Boulton and James Watt built the steam engines that powered the industrial revolution. There's also a basin at the northern entrance to the Avery Arm with an impressive chimney and a bricked up horse doorway which is reached after the canal dips under the Avery (Soho) Rail Bridge.
Opposite is French Walls which housed Muntz's Metal Works. George Muntz made a fortune producing sheet metal from a patented alloy of copper and zinc that was used for boat hulls, including the Cutty Sark, as a cheaper and more effective alternative to pure copper. Next to the foundry was Smethwick Gas Works initially established by William Murdock c.1805, the country's first commercial manufactured gas works. Further on was Tangye's Cornwall Engineering Works, built on the site of Rabone Hall, which produced the hydraulic presses and jacks used to launch Brunel's 'Great Eastern' after it had been stuck on the side of the Thames for several weeks. Their equipment was also employed in the construction of the Sydney Harbour Bridge, Spaghetti Junction and the Thames Barrier. Until the 1960s Ernest Thomas boats had to negotiate the Cornwall Arm or 'Tangye's Hole' to take rubbish from the works to the dump at Moxley but, as there was no tow path, their horses had to be left on the main line while the boats were manhandled to the loading basin.
Bear right following the Old Main Line at Smethwick Junction to Smethwick Locks which had to be constructed due to the geological difficulties of building a tunnel. However, there was a constant lack of water and two steam engines were put in place to pump this precious resource from the bottom of the locks back to the 491ft summit. The first in operation was at Spon Lane in 1778 and then the original Smethwick Engine came into service in May 1779. It was the first in the world to utilize James Watt's innovative system of using the vacuum created in a separate condenser to maximize a steam engine's power. It worked fairly well, together with a second engine installed in 1804, lifting 1700 gallons of water every minute, twenty four hours a day for over a hundred years. When maintenance became too problematic, a replacement was installed in the re-located Smethwick Pumping Station (1892) and that is the building that you can see today. The new engine's two pumps could transfer 200 lockfuls of water per day from the new to the old main line. However in 1905 one pump set was transferred to the Walsall Canal and, due to declining traffic, the remaining set became redundant by around 1920 and was sold off. The original Boulton and Watt engine, the world's oldest working example, is now displayed in Birmingham's Thinktank.
Another improvement, overseen by John Smeaton and completed by 1790, was lowering the summit to 473ft and halving the number of locks, with a duplicate set of locks inserted at the Smethwick end to deal with the high volume of traffic, which are the ones that survive today. The original Brindley locks that can still be discerned were filled in during the 1960s.
Further water was delivered by Telford's magnificent Engine Arm Aqueduct, a 52ft long iron trough supported by a highly decorative cast iron arch. Completed in 1825, it is Grade II* listed and towers over Telford's New Main Line. The Engine Arm's original purpose was to deliver coal to the Smethwick engine, the reason for the aqueduct was to feed water from Rotton Park (Edgbaston) Reservoir, created by Telford between 1824-1829, to which the arm had been extended, although the walker can only explore a short distance until reaching private moorings.
After the Summit Tunnel, there's a pleasant stretch that includes the remains of the coal wharf that served the (Diamond) Jubilee Colliery about two miles away that closed in 1960. A tramway carried coal in wagons from the pit and then it was sent by chutes down the embankment to the waiting boats. Any thoughts that you've entered a rural idyll are run over by the M5, and the environment becomes dark and claustrophobic. Crossing over Spon Lane Bridge you are hemmed in by motorway pillars but bear right and daylight returns along Spon Lane Locks, reputed to be the oldest working locks in the world, where the canal falls 20ft to Bromford Junction. Once busy with Clayton's tar boats and others carrying coal from Sandwell Wharf, these locks are now a backwater lined with blackberry bushes.
Turn left at the junction onto the New Main Line and huge columns supporting the M5 occupy the middle of the canal. After going under the Stewart or Steward Aqueduct carrying the Old Main Line, there's plenty to keep your interest on the way back to Smethwick Junction. The derelict buildings that you pass on the left are where Chance Brothers were based for 150 years, innovative glassmakers who glazed the Crystal Palace, the four faces of Big Ben and lighthouses throughout the world. Where there is a lighthouse, there is probably still Chance glass.
Following Spon Lane Bridge a more verdant landscape takes over and birds try to make themselves heard above the rumble of the motorway. Galton Bridge (1829) and Tunnel are then reached, the bridge is a single span of 151 feet and was once the highest in the world, the tunnel by contrast is boring modern concrete finished in 1974. Then, just before the Smethwick Stop, you have the privilege of admiring from below the finely detailed cast iron of the Engine Aqueduct, judging from this magnificent edifice they don't make bridges like Telford did any longer. Just after the aqueduct there is an elevated bench where you can take a break.
After Smethwick Junction and Towing Path Bridge, industry kicks in with a vengeance. Take the less travelled right hand towpath back to the City Centre. You are less likely to be run down by a speeding cyclist and you'll have a good view of the Soho Foundry before the landscape very gradually becomes greener, with trees lining the towpath and elegant Horseley Bridges decorating the canal. Just before Rotton Park Junction you'll see the remains of a bridge that carried the Harborne Branch of the LMS over the canal until 1963 and above, but out of view, is the feeder that takes water from Rotton Park Reservoir to the Engine Arm.