The border between Gisenyi and the Congolese city of Goma runs straight through the middle of what is effectively one continuous urban area, and the crossing at the Grande Barrière is open to pedestrians during daylight hours. Day trips across to Goma are possible — the Rwandan government has relaxed visa requirements considerably — but the security situation in eastern DRC can change rapidly and it is worth checking the current picture before crossing.
Goma itself, sitting at the foot of the still-active Nyiragongo volcano with its lava plains and UN presence, is a remarkable place — chaotic, energetic, and unlike anywhere else in Africa. The view of Nyiragongo from the Goma side on a clear evening, with the glow of the lava lake visible at the summit, is hard to forget.