Noteworthy locations provide our characters somewhere to stumble upon, avoid, or seek out on missions. They can cause interesting items or life forms to exist, possess, or flee from. World builders can place these in almost random locations, reducing the burden of logic needed to explain origins. Some phenomena simply exist where they do or are the result of natural geological forces (such as volcanoes or meteor strikes), while events such as explosions, battles, or experiments gone awry can cause others. Used in small doses, they can add complexity, interest, and variety to a setting.
Not every location needs to be spectacular to be of interest. Anything unusual can do and should not be overlooked.
Catacombs and Hidden Passages
Catacombs, bomb shelters, sewer lines, tunnels, and subway lines, especially beneath a settlement, can provide somewhere to hide people, creatures, or possessions, and be used for stealthy maneuvering. We can decide they are known to all or a select few who are using them for nefarious purposes. Even if known, the extent of them seldom is; much of the fun lies in the mystery. When inventing these, decide why they exist. They might have been designed for covert work, such as in military locations. Royalty could have decided they wanted ways to move about without being noticed (or for their spies). Excessive heat in tropical locations might have led to these cooler places to dwell at times, or store things like wine or munitions. Perhaps there are secret training facilities.
In a world with dwarves, perhaps they just enjoy such locations as a reminder of home and have tunneled deep, with or without permissions. They might no longer live here, leaving abandoned tunnels that are partly in use by those with both good and bad intentions. Sometimes these locations aren’t known because a civilization or population from a thousand years ago might have left it. The current settlement could even have been built atop such a place with no one realizing it.
Step Wells
For most of us, a water well might not sound interesting, but if you Google “step wells in India,” the pictures will change your mind. These are elaborate pits in the ground with flights of stairs leading down to the water. The steps appear akin to an amphitheater, being wide and often on all four sides in a square or rectangular shape. Platforms can exist in these, and with some imagination, we might decorate them with carvings and statues. Some structures have cave-like openings into a cliff face and buildings that are carved from within. If we have a species which dwells in fresh water, they may swim up underground rivers to emerge from these wells.
Monuments
Monuments can be buildings, monoliths, or statues. Some could be more spectacular than others and qualify as famous locations. This can be due to size, complexity, or the individual or occasion being memorialized. Having world figures helps us decide on the latter. We should also determine the condition such monuments are in. Those in abandoned places might be in disrepair or have been vandalized, even destroyed utterly, whether this is known or discovered by characters in a story. Visiting such a place to acquire power or an item can therefore throw characters off their intended quest. Monuments located amid existing civilization might also be prone to thievery attempts and desecration.
On Earth, we have Egypt’s great pyramids, the Great Wall of China, or Stonehenge. The ancient world included the Seven Wonders, which included a temple, two statues, the pyramids, a mausoleum, gardens, and a lighthouse. These seven were chosen because there were, at the time, seven bodies in the heavens: the sun, moon, and five discovered planets. An invented world might benefit from a similar explanation if monuments are being counted. The lists can be longer, and different lists have existed over time. The original seven don’t sound impressive until one considers the unusual size, adornment, or subject (often a god) of most. Many of these wonders were destroyed by earthquakes or floods.
Graves
While most cemeteries won’t be of much interest, other burial sites may be. One possibility is a system of catacombs, where skulls and bones have been stacked. Mausoleums can be enormous, uniquely decorated, or house famous people; these may contain items, such as treasure, which others plunder. These would require guards of ordinary or extraordinary kind, such as ferocious animals/monsters, or humanoids with demonic, technological, or magical powers. Graveyards could also have unique layouts where different classes of people are interred separately. Rituals might also be done at regular intervals. A day of the dead festival might exist, the macabre scene fitting for a story. Lone grave sites in the wilderness might also achieve significance for location or features.