Reflection

Fence... Boundaries...Walls...Floors... Tunnels... they all stop entry and create enclosure...
Trying to cross these barriers is the adventure! It's what creates the fear of taking the risk and therefore the thrill... Entering spaces without having any knowledge of what to expect is that thrill... It's the exploration of the spaces and learning new things

This can be evolved into the idea of discovery and adventure... Experiencing different environments and overcoming the fear of exploring the unknown...
These can be taken as physical experiences for example different areas of the world; different countries, different environments, different atmospheres...
Or it can be taken as emotional experiences such as happiness, fear, sadness, excitement, surprise... all unlike feelings, emotions and therefore different experiences... all unknown and scary territories the first time they are experienced...

The physical environment can alter these emotional experiences... for example the light in a room can make people feel happier and excited... the darkness in a room can create fear and sadness etc.... and the boundaries between these spaces are important as the boundaries 'define' the spaces...

It's all in the experience!