Gaudí took forty-three years of his life on the Sagrada Família and still did not see it finished. He began work in 1883, soon after taking over from another architect, and from the 1890s onward he devoted himself to it almost completely, living in a workshop on site in his last years. The Nativity Façade, on the east side, is the part that he built the most of, and it was the only one to be substantially completed in his lifetime. Its carved portals teem with plants, animals and figures, tortoises at the foot of its columns included, and the effect is like a cliff of stone coral.
Underneath is the crypt where Gaudí himself is buried, after being hit by a tram in 1926 and, at first, not being recognised because he was so shabbily dressed. The crypt was the first part of the church to be built and is much quieter than the nave above, a plain Neo-Gothic space with the architect's tomb in a side chapel. UNESCO has listed the façade and crypt with other works by Gaudí in Barcelona, and it is worth seeing them in daylight.
As for the riding, this is not a place to cruise. You are in the middle of Barcelona's grid, and the best approach is to arrive early, park the bike in one of the designated motorcycle bays on a nearby street, and walk. Traffic is dense and the cobbles are slick when wet, and tourists step off kerbs without looking. Check the rules for the city's low-emission zone before you go, as older bikes may be restricted, and keep your belongings with you, because Barcelona has a well-earned reputation for bag theft.
There is a good reason to come, though. A rider who has spent days in the empty hills of Valencia and Aragon will find that the contrast gives the city extra force. Pause on the pavement outside, look up at the towers and take in the shock of its detail. Fuel is available at several stations around the city, and the cafés nearby serve everything from strong coffee to a plate of tapas. Weekday mornings are the quietest time to visit.