Here a number of places you can visit from Tokyo if you’re looking for a day trip.
Kamakura: A small city about an hour by train from Tokyo famous for it’s temples, beach, and Giant Buddha. From Tokyo Station, take the JR Yokosuka Line to Kamakura Station.
Hakone: A mountainous area west of Tokyo, 1-2 hours away by train. Famous for its hot springs, scenic views, relaxed atmosphere and giant shrine. Take the Odakyu Odawara Line from Shinjuku station.
Yokohama: A port city about 30 minutes from Tokyo. Check out Chinatown, the Ramen Museum, or take a lift to see a view of the city from the 69th floor of the landmark tower.
Hitsujiyama Park (April-May): An amazingly scenic park located in Saitama. Take the train from Ikebukuro station for about an hour.