In 2006 I took a trip to Seville, Spain to observe the famous Feria de Abril or April Fair. This traditional celebration of spring comes only two weeks after the city has celebrated another huge festival, the observance of Semana Santa or Holy Week. There are so many traditions revolving around the Feria that it takes a book to describe them all.
April is a good time to visit Seville, not only because of the Feria but also because of the comfortable temperatures of that season, with highs typically in the 80s. Seville can get really hot in the summer, and 110 degrees Fahrenheit is not uncommon.
The most famous building in Seville is the cathedral, with its adjoining Giralda tower. The cathedral is huge - one of the largest in the world - and features artifacts of all kinds in addition to the altars, stained glass windows and other things you would expect in a church. The tower is actually older than the cathedral itself, as it dates back to the 13th century and was originally a Muslim minaret. The original top was destroyed in an earthquake and was eventually replaced by an ornate bell tower in the 16th century, but it blends well with the rest of the tower. The picture gives a good idea of how well lit this part of the city is and in particular the Giralda tower.
See my webpage on Spain at http://www.latinandcaribbeantravel.com/spain.html