The terrain to be crossed was problematic for the canal engineers, as demonstrated by the several proposals made for routes. The core of the problem was the lack of river valleys or other obvious routes to take. The undulating countryside meant that the chosen route needed many twists and turns to maintain a level. However, the route does not keep as strictly to contours as the early canals of James Brindley did; the worst potential diversions were avoided by cuttings, embankments, and two significant tunnels, one of at Crick and another of at Husbands Bosworth, both of which were wide enough for narrowboats to pass.