A dream about seeing a portal but not touching it or walking through it signifies that you have an urge to explore and escape the mundane day-to-day life you are currently leading. It is an idea of hope, fear, curiosity and escape.
If you dream of touching or are traveling through a portal, it indicates that you have an imposing presence in your life that you are still undecided about. It could be a person, new opportunity, or challenge you are facing but it is very imposing.
Traveling through a portal and coming out safely at the other side means that you are in search of higher consciousness.