Complex sentence: It lays claim to being the site of the oldest riverside tavern, dating from around 1520, it was formerly known as the "Devil's Tavern", all that remains of this period is the 400 year old stone floor.
Split into simpler sentences: It lays claim to being the site of the oldest riverside tavern, dating from around 1520. All that remains from the pub's earliest period is the 400 year old stone floor.