On a budget, Montserrat (day-trip) still earns its price.
€€ (~€30 train+railway return)
A Benedictine monastery wedged into surreal sawtooth peaks, home to the revered 'La Moreneta' Black Madonna and the famous boys' choir, with cable-car or rack-railway ascents and hiking trails along the ridges. It's the classic, spiritual day out. The catch: it's a half-to-full-day commitment with train-plus-mountain-railway transfers, it gets very crowded midday, and the monastery itself is small.