The Castillo de San Gabriel is a small 16th-century fort on an islet just off the Arrecife seafront, reached on foot across the much-photographed Puente de las Bolas. It now houses the city's Historical Museum, with collections covering Arrecife's history from the early Spanish conquest through its emergence as the capital of Lanzarote in the 19th century.
The museum is small and quickly visited, but the islet and bridge are worth the walk regardless. The view back toward the seafront is one of the prettiest in the city.