Lovely swiss restaurant with great quality food for a good price! Best known for their huge cordon…read morebleus which can be ordered with different fillings such as onions, bacon, truffle, pineapple and more. See the menu here (only in german): http://www.national-burgdorf.ch/pdf/speisekarte.pdf
It is situated about 10 walking minutes from the railway station. On warmer days you can sit outside on the patio, which is surrounded by green. It's not the quietest, because the roundabout is just some metres behind the hedge. Some places on the patio are under the open sky, some under a roof.
The food is awesome! I already went there three times and ordered a cordon bleu every time. Take the big one (500gr.) even when you know in advance, you won't be able to eat the whole. The staff is happy to wrap it up in aluminum foil, so you can take it home. The difference to a smaller, even big, cordon bleu is 5-7 CHF, so it's up to you. I already had the Lothringer-Cordon bleu, the Saisonhit and the one with truffles and all of them tasted fantastic! The meat is best quality and CHF 34.- for half a kilogram is still a good price! The gratinée carrot-ginger soup as an appetizer was great. If you have some air left in your stomach after the cordon bleu, try the trilogy of desserts, which are varying from time to time.
Enjoy your stay there and let me know if you took some of my recommendations and if you agree with me :-)