Eureka is a small city and Old Town is very walkable — the historic district, waterfront, and most restaurants and sights can all be reached on foot from a central hotel. For anything beyond downtown, a car is necessary; Sequoia Park Zoo and Blue Ox Millworks are both a mile or more from the waterfront.
By bus: Eureka Transit Service (ETS) operates local routes within the city. The Humboldt Transit Authority (HTA) runs regional routes including a frequent connection to Arcata.
By car: Parking in Old Town is generally easy and cheap, even in summer. The main complications are the one-way grid through downtown and occasional congestion on 101 during the summer weekend afternoon rush.
By bike: The city has bike lanes on some downtown streets and a flat waterfront area. The Bay Trail along the waterfront is pleasant for cycling. Rentals are available from a few shops near Old Town.