As of now, the virtual currency market in the Greek city of Thessaloniki is still in its early stages, with only a few exchanges operating in the region. However, the largest virtual currency exchanges in Thessaloniki are:

1. Coinomi: Coinomi is a popular multi-asset digital wallet that supports a wide range of cryptocurrencies, including Bitcoin, Ethereum, and Litecoin. The platform also allows users to exchange different cryptocurrencies within the wallet itself, making it a convenient option for traders in Thessaloniki.

2. Bitstamp: Bitstamp is one of the oldest and most reputable cryptocurrency exchanges in the industry. Founded in 2011, Bitstamp offers a secure platform for buying, selling, and trading a variety of digital assets. The exchange is known for its strong security measures and user-friendly interface, making it a top choice for traders in Thessaloniki.

3. Kraken: Kraken is another popular cryptocurrency exchange that has gained a strong reputation for its security features and wide range of trading options. The platform supports a variety of cryptocurrencies, including Bitcoin, Ethereum, and Ripple, and offers advanced trading tools for experienced traders. Kraken's user-friendly interface and responsive customer support make it a top choice for virtual currency enthusiasts in Thessaloniki.

While these exchanges are currently the largest in Thessaloniki, the virtual currency market is constantly evolving, and new exchanges may emerge in the future to cater to the growing demand for digital assets in the region. As the adoption of cryptocurrencies continues to expand in Thessaloniki, we can expect to see more exchanges entering the market to meet the needs of local traders and investors.