The central, flatter part of the canton of Berne is marketed as the Swiss Mittelland by the Swiss tourism office. This region includes the northern part of the canton of Berne, the German speaking part of Fribourg as well as the southern half of the canton of Solothurn.
The northern part of the canton around the Swiss capital Berne, whose old town is inscribed as a UNESCO world heritage site. Biel is a bilingual city famous for being home to many watch companies. This is also were the picturesque Emmental is located, home to the famous cheese.
South Solothurn (Solothurn 📍, Olten 📍)
The capital Solothurn is a small town at the southern edge of the Jura mountains, but the largest city is Olten. The northern part of the canton is part of Northwestern Switzerland
Sense District (Düdingen 📍, Schwarzsee 📍)
This is the German speaking part of the canton of Fribourg (also called Freiburg). The French speaking part is part of Western Switzerland. The area is mostly known for the Schwarzsee resort and lake, surrounded by the Gantrisch nature park.
The public holidays are different in each canton. These are the public holidays in addition to those observed in the whole of Switzerland:
In the canton of Solothurn many towns have their own local holiday on the day of their saint patron.
There is an airport in this region, near the city of Berne. However, as this airport doesn't offer that many connections, for most travelers it will make more sense to take the plane to Zurich.
Related Wikipedia article: Bern-Mittelland (administrative district)