|Locks, aqueducts, and a tunnel
Perhaps the most interesting surviving features of canals are the locks, (where sections of the waterway at different heights are connected) and aqueducts (where the canal is carried over rivers or valleys).
|The Brecon and Abergavenny Canal is just over 33 miles [53km] long, but it was built by following the shape of the land where possible, so that only six locks were needed. Although this made the canal longer it saved on the cost of building locks and also reduced delays to boat traffic.
|One of the
set of five of these locks at
is shown in the fairly recent photograph above. A 23 mile [37km]
section of the canal stayed on one level,
even though it passes through very hilly countryside.
There is an impressive four-arch aqueduct where the canal passes over the River Usk at Brynich, just below Brecon. It is shown in the old photograph on the left and on the 1888 map section on the right.
The line of the canal
also features another aqueduct at Gilwern,
which has only a single arch but is very high. This was part of a large
embankment which crossed over the River Clydach
and one of the early tramroads.