Advanced Property Valuation Machine Learning Pipeline Design

Design a comprehensive machine learning architecture for predicting real estate property valuations using multiple data sources. Create a detailed workflow that integrates historical sales data, neighborhood economic indicators, geospatial analysis, and predictive modeling techniques. Include specific feature engineering strategies, model selection criteria (random forest, gradient boosting), and a step-by-step implementation plan with cross-validation methodology. Provide pseudocode demonstrating how different data sources will be weighted and integrated into a final predictive score.