Ten kilometres northwest of Vejle, in the small town of Jelling, stand two runic stones that are arguably the single most important historical monument in Denmark. The smaller stone was raised by King Gorm the Old in memory of his wife Thyra, making it Denmark's oldest runic inscription. The larger — raised by their son Harald Bluetooth around 965 AD — bears a carved image of Christ and an inscription declaring that Harald "made the Danes Christian." Together, they mark the moment Denmark officially converted from Norse paganism to Christianity. The larger stone is sometimes called Denmark's birth certificate.
The stones stand in the churchyard of Jelling Church, flanked by two enormous Viking burial mounds — the largest in Denmark — that predate the church and were probably the burial site of Gorm and Thyra. The complex is a UNESCO World Heritage Site. The adjacent Kongernes Jelling museum (open daily, free entry to the grounds) provides context and shelter from Danish weather. The stones themselves stand outdoors, and you can get close to them and examine the carvings directly. Plan an hour, more if you visit the museum.
Getting there without a car is straightforward: buses run from Vejle bus station to Jelling. The journey takes around 20 minutes. The site is well signposted from the main road.