St. Goar is a small river town directly below Rheinfels Castle on the left bank of the Rhine, connected to the opposite town of St. Goarshausen by the Lorelei ferry. It is the quietest of the main Middle Rhine towns — not as polished as Bacharach, not as large as Boppard — but the combination of the enormous castle ruin above and the river traffic below gives it a particular character.
The town has a pleasant waterfront, a few good restaurants, and direct train access from Koblenz and Mainz, making it the most practical base for exploring both Rheinfels and the Lorelei rock (reached by ferry to St. Goarshausen and then a short climb). The twice-hourly rail service means you can move easily up and down the valley without a car. In summer, the river ferries from Cologne and Rüdesheim stop here.