Although I am living in Valencia as a student, I have had several people come to visit me, and when they are here, I can play tourist for the day. The variety of things to do in Valencia is truly staggering. If you like the city, the beach, or the countryside and mountains, Valencia has something for you. This makes it an ideal holiday destination for someone who wants the opportunity to see a bit of everything, or for a large group that does not mind splitting up at times so people can enjoy what they specifically want to do.
The centre of the old city is stunningly beautiful, with wonderful architecture and lots of small streets that you can get lost in for hours (this is not an exaggeration, take a map with you!). There are lots of offers for free walking tours which tend to meet in la Plaza de la Virgen. It is definitely worth going on one of these tours because the guides are brilliant, you decide whether you want to pay in the form of tips, and the whole experience sets you up well with an idea of what you might want to see in more depth later on in your stay. If you are interested in science and culture, you have to visit the Ciudad de Artes y Ciencias. Even if you only go by metro, and walk through the sunken river garden to look at the buildings, it will be well worth it. The architecture alone is reason to visit, before you have even gone inside. If you go to the Corte Inglés nearby, the restaurant is on the 8th floor and offers a beautiful view over the whole complex, if you manage to get a window seat.
There are a lot of opportunities for shopping, eating and drinking in the old city and further out. In the centre, you can find some tourist traps, with overpriced, mediocre food, so be savvy and check online for reviews of places beforehand. The Spanish are particularly proud of their food and its diversity, so make the most of this. Some particular Valencian specialties are: a proper Valencian Paella, which should have chicken, rabbit and snails; horchata, which is a refreshing non-alcoholic drink made from chufa nuts, water and sugar; fartons, which are long, thin rolls of enriched dough, sprinkled with sugar and designed to be served with horchata, for dipping (vegetarians, do be aware that traditionally these are made with lard, so check before ordering).
Valencia is a coastal region, and the beach is a gorgeous stretch of pale sand and intensely blue sea and sky. There are plenty of places to eat here too, of course, and the air is intensely fresh. Something I immediately noticed when I went was the absence of the seaweed smell that I automatically associate with British beaches, and it was a really nice change.
If you have a car, and are prepared to drive a couple of hours, it is worth it to go to some of the mountains and the smaller towns there. There are lots small towns, for example Montanejos, which is nestled in the mountains, with the river running through it, and the walks here are stunning. Rosemary grows all over the place, and people come from all around to bathe in the river.
Accommodation-wise, there are options for all budgets and styles. The possibilities are endless!