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' which is really an extended bridge, passing the ICC along a towpath full of shoppers and tourists. Then go left in front of the Sea Life Centre and over the Oozells Street Loop (that leads to Edgbaston or Rotton Park Reservoir) at Deep Cutting Junction aka Old Turn with its unique island sign post.
From here this is a walk along the Birmingham Main Line (new and old) on either side of the canal towards Wolverhampton. 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 are turning it into 'a hub from which to explore the city'. Passing Monument Road Basin (a former railway interchange), you'll reach the start of Icknield Port Loop. This is one of the many 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 and a neat housing estate. All but hidden on the other side is the City Hospital. 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 Brimingham, 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 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 esablished 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 initally 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 hydraulic presses and jacks, and adjacent was Woodford Iron Works. All of these factories had their own basins, some of which are more visible today than others.
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, overseen by John Smeaton, the summit was lowered and the number of locks halved, 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.
Another solution was to employ a pump to lift water from the new main line to the old level. The original Smethwick Engine which came into service in May 1779 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 Smethwick Pump House (1892) and that is the building that you can see today. The original Boulton and Watt engine, the world's oldest working example, is now displayed in Birmingham's Thinktank.
Further water was delivered by Telford's magnificent Engine Aqueduct, an iron trough supported by a highly decorative cast iron arch completed in 1825. This leads to the Engine Arm that can be explored until you reach private moorings, its purpose was to feed water from Rotton Park (Edgaston) Reservoir to the summit level.
After the Summit Tunnel, there's a pleasant stretch and even a nature trail. But 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.
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 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.
After Smethwick Junction and Towing Path Bridge, industry kicks in with a vegenence. Take the right hand towpath back to the City Centre 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.