Items such as fine wines, Gold, Art, antiques are often known as tangible assets, leaning legally they can be touched. They are often rare and well sought after, and the less of them in existence the greater their value can rise.
Fine Wines for example. If a particular wine was in demand and classified by experts as one of the best, for that year, it’s price may be worth £100 per bottle. 5 years later, if most owners have drunk theirs, you may find your bottle of wine is now worth double its value or more. You often see vintage ports and whiskeys from the 1800s go for hundreds of thousands of pounds, again, depending on their condition, age, manufacturer and how many are left in existence.
Arts and collectables often seem to go up in value, again you need to know plenty about this world. Tastes can change often, as well as can fashion so it’s always a good idea to keep an eye on the trends.