Castellón de la Plana is a charming city located on the Mediterranean coast of Spain, known for its historic landmarks, beautiful beaches, and rich cultural heritage. If you're planning a day trip to this city, here are the top 10 tourist attractions you should consider:

1. Castellón Cathedral: This impressive Gothic-style cathedral dates back to the 13th century and features stunning stained-glass windows, intricate stone carvings, and a towering bell tower.

2. El Fadrí Tower: This iconic tower is one of the most recognizable landmarks in Castellón de la Plana and offers panoramic views of the city and the surrounding countryside.

3. Central Market: This bustling market is the perfect place to sample local cuisine, including fresh seafood, fruits, and vegetables, as well as traditional pastries and sweets.

4. Llotja del Cànem: This beautiful Renaissance-style building was once a center of the city's trade and commerce and now houses art exhibitions and cultural events.

5. Planetarium: This state-of-the-art planetarium offers visitors the chance to explore the cosmos through immersive shows and interactive exhibits.

6. Provincial Archaeological Museum: This museum showcases the rich history and culture of the region through a collection of ancient artifacts, including ceramics, sculptures, and Roman mosaics.

7. City Hall: This stunning neoclassical building is one of the most impressive examples of architecture in Castellón de la Plana and features a grand staircase and ornate ceilings.

8. Playa del Gurugú: This beautiful beach is located just a short drive from the city center and offers golden sand, clear blue waters, and plenty of opportunities for sunbathing and swimming.

9. Basilica of Our Lady of Lledó: This Baroque-style basilica is dedicated to the patron saint of Castellón de la Plana and features a stunning altar, ornate chapels, and intricate frescoes.

10. San Miguel Plaza: This charming square is surrounded by colorful buildings and features a beautiful fountain, as well as plenty of outdoor cafes and restaurants.

These are just a few of the many attractions that Castellón de la Plana has to offer, and there's plenty more to discover in this vibrant and historic city.

The distance between Castellón de la Plana and Oropesa del Mar is approximately 23 kilometers (14 miles) by car. The driving time may vary depending on traffic conditions, but it usually takes around 25-30 minutes to travel between these two locations.