You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Valencia

Context:
Valencia has experienced a surge in its cultural development during the last thirty years, exemplified by exhibitions and performances at such iconic institutions as the Palau de la Música, the Palacio de Congresos, the Metro, the City of Arts and Sciences (Ciutat de les Arts i les Ciències), the Valencian Museum of Enlightenment and Modernity (Museo Valenciano de la Ilustracion y la Modernidad), and the Institute of Modern Art (Instituto Valenciano de Arte Moderno). The various productions of Santiago Calatrava, a renowned structural engineer, architect, and sculptor and of the architect Félix Candela have contributed to Valencia's international reputation. These public works and the ongoing rehabilitation of the Old City (Ciutat Vella) have helped improve the city's livability and tourism is continually increasing.

Question:
What part of Valencia is undergoing improvements?

Old City