BARCELONA, Spain — Hundreds of thousands of pro-independence Catalans took over downtown Barcelona on Tuesday, in their largest show of force since a botched declaration of independence from Spain last October.

The rally on Catalonia’s national day, known as the Diada, was peaceful as the demonstrators deployed along almost four miles of the Diagonal, the main avenue that cuts across Barcelona. Many wore fluorescent pink T-shirts with a drawing of a mountain and the slogans “Let’s make the Catalan Republic” and “Straight to the peak.”

Still, many demonstrators acknowledged that the path toward independence looked more like a long and winding road than a straight-to-the-top ascent, particularly after last October’s turmoil.